Why does a child have a low-grade fever for a long time? Why does the temperature persist after an acute respiratory infection?

A woman’s body is a rather complex structure of various relationships. Throughout her life, her body grows, develops, and certain transformations occur. There are also changes in hormonal levels. The causes of low-grade fever in women are different, some of them are the same for both women and men, but, naturally, there are also purely individual ones.

• Having reached puberty, the balance of hormones can change depending on the phase of the menstrual cycle. Therefore, it is quite normal that immediately before menstruation, temperature indicators can increase.
• Pregnancy period. Temperature fluctuations are also possible during the period when a representative of the fair sex is preparing to become a mother, carrying her baby. This is also due to hormonal changes in the body.
• A respiratory viral infection can cause a similar symptom. After the acute period of the disease has passed, the presence of low-grade fever indicates that the inflammatory process has not yet been completely stopped and the fight against the virus has not been completed. Therefore, even if the symptoms of ARVI have gone away, it is imperative to continue treatment. In this situation, it would be a good idea to make an appointment with a specialist (otolaryngologist). If there are no symptoms, the doctor may prescribe an examination, for example, a throat swab to check for the microflora present. This will allow us to determine the extent of the pathological invasion. In the normal course of an acute respiratory disease, fever can persist for up to five days, if there is no reduction, therefore, the disease continues in the form of complications. Additional diagnostics and adequate therapeutic treatment are necessary.
• Persistent low-grade fever; defect of the hypothalamus and pituitary gland. It is these areas of the human brain that are responsible for fluctuations in body temperature. Unreasonable low-grade fever can indicate that the functioning of these areas is malfunctioning and differs from the norm. If this cause of deviation is suspected, the specialist prescribes magnetic resonance imaging (MRI) to the patient. One of the reasons for their failure may be a developing tumor neoplasm.
• Another reason for the appearance of the symptoms in question may be severe pathology of the thermoregulatory organs. A thorough substantive examination and treatment, and in some cases lifelong maintenance therapy, are necessary.
• Severe stress experienced can also cause the appearance of low-grade pathology.
• Dental diseases, such as caries.
• As medical statistics testify, the modern population, especially large cities and metropolises, suffer from neuroses to one degree or another. Nervous stress affects not only the psyche of people; the entire body also suffers from strong emotional overexcitation. Sometimes the nature of some manifestations is quite difficult to determine. For example, a person complains of discomfort in the throat and begins to treat it with antiviral drugs - the result is zero, since the cause of soreness may be a nervous shock. Therefore, if, against the background of low-grade fever, there is irritability, a sharp change in mood, a feeling of anxiety and sleep disturbance, then these are clear signs indicating that the fever can persist as the body’s reaction to neurosis.
• If the readings on the thermometer increase in the evening, vegetative-vascular dystonia (VSD) can provoke such a clinical picture. This diagnosis covers a fairly wide range of diseases associated with the vascular system of the brain. But a more specific diagnosis can be obtained after a systematic examination.
• Mostly, the source of low-grade fever is chronic infectious lesions of the ENT organs and the genitourinary system. If a person has a history of, for example, cystitis or tonsillitis in the chronic stage, then the risk of recurrent activation of pathogenic microorganisms increases significantly. A relapse provokes an exacerbation of the disease and an increase in temperature indicators.
• Low-grade fever may be a consequence of the recovery period after therapeutic treatment for pneumonia. But if x-rays and blood tests do not show any abnormalities, then there is no need to worry. Gradually everything will normalize and return to normal.

Causes of low-grade fever in children

Every person knows from childhood that the normal human body temperature is 36.6. But doctors are not so categorical and allow the norm to be up to 37.0 o. But if a child’s thermometer shows numbers from 37.0 to 38.0 °C for several days in a row, then this fact begins to seriously worry parents. It is interesting that such indicators can remain in the baby for a month, without being accompanied by other negative symptoms. During this period, the child feels absolutely normal and leads an active lifestyle.

If this situation has been observed for at least two weeks, doctors begin to talk about low-grade fever - a medical situation in which the clinical picture is characterized by a single symptom - and this is low-grade fever. This reaction of the baby’s body should not be ignored. After all, it indicates the presence of some kind of failure, which, it is desirable, can be quickly identified and the necessary measures taken.

The causes of low-grade fever in children are different, but some of them can be mentioned:

• Hidden infectious lesions of internal organs.
• An allergic reaction of the baby’s body to any external irritants can also cause such a symptom.
• Increased activity of the thyroid gland, which produces an excess of enzymes, can also provoke an increase in temperature indicators.
• The source of high temperature can be infestation of protozoa, for example, worms.
• Low levels of hemoglobin or red blood cells in a child's blood (anemia) often cause temperature fluctuations.
• Failures in the functioning of metabolic processes, for example, in diabetes mellitus, can also cause symptoms.
• Diseases affecting children's brain structures.
• A severe form of vitamin deficiency, especially regarding the lack of vitamins such as C and the entire spectrum of group B in the baby’s body.
• Congenital or postnatal malfunctions of the immune system.
• Thermoneurosis is a condition in which a violation of natural thermoregulation occurs in the body of a small patient, that is, the child’s body produces more heat per day than it manages to use. It is this excess that causes low-grade fever. Such a malfunction can occur if there is a disruption in the functioning of the endocrine system or the thermoregulatory center located in the brain.

It should be remembered that low-grade fever is not relieved by antipyretic drugs. And the problem is not even that it is useless and does not give any effect, it also weakens the defenses of the small organism, worsening its ability to resist and fight the disease.

In such a situation, parents are required to monitor the baby’s body temperature for some time; it would be a good idea to record these indicators in a notebook. This approach will allow the specialist to better assess the situation. If the temperature remains high for several days in a row, then you cannot do without consulting a pediatrician.

The doctor will prescribe a general examination and, after receiving its results, will be able to give the necessary recommendations or prescribe treatment therapy. Doctors believe that it is necessary to treat this pathology. After all, any deviation from the natural functioning of a child’s body is stress for him.

In addition to drug treatment, if necessary, parents can help their child by organizing the correct daily routine for him, which will include moderate exercise and proper rest, including normal, long sleep. Not the least important place is given to hardening the baby’s body - this will help relieve many problems with the child’s health. Physical training will also be beneficial for strengthening the body. You just need to adhere to the systematic implementation of such procedures, otherwise you may not see the desired result. Hypnosis and acupuncture are practiced with such a clinical picture.

Causes of prolonged low-grade fever

A low-grade symptom is a reading on a thermometer ranging from 37 to 38 ˚C. Its prolonged manifestation is a fairly common complaint with which patients seek consultation with a specialist. The causes of prolonged low-grade fever can be different; to establish them, the patient must undergo a full examination.

Quite often, low-grade fever is observed in young women against the background of increased fatigue, exhaustion of the body with all kinds of diets, weakening or loss of the ability for prolonged physical or mental work. This fact is explained by the physiological individuality of the woman’s body. It is women who show a high level of infectious damage to the urogenital system, and it is the female body that is exposed to multiple psycho-vegetative disorders.

It should also be understood that long-lasting fever is very rarely provoked by an organic disease. Mostly, this symptomatology reflects classic autonomic dysfunction - the disease is caused by a symptom complex of disorders of autonomic, sensorimotor and psycho-emotional activity.

Sources that cause long-term manifestation of the symptom in question are divided into two groups: non-infectious and infectious pathologies.

Such infectious diseases include:

• Tuberculosis. When a high temperature appears, which is observed for a long period of time, the first thing doctors do is to exclude from the list of possible causes of the pathological manifestation of such a terrible disease as tuberculosis. This is not always easy to do. When identifying anamnesis, the doctor must find out whether the patient has had contact with a patient suffering from an open form of tuberculosis.
• If the patient has a history of treated tuberculosis. This disease is dangerous because it shows a high rate of relapses. It could also be a poorly treated disease that was treated over the next three months.

In the presence of one of the forms of tuberculosis, in addition to prolonged low-grade fever, additional symptoms can be observed:

• General intoxication of the patient's body.
• Fatigue and weakness.
• Increased activity of the sweat-secreting glands.
• Decreased appetite.
• Losing weight.
• A cough that lasts more than three weeks is a sign of pulmonary tuberculosis. This may also include the appearance of shortness of breath, expectoration of blood, and pain in the chest area.
• Complaints about the normal functioning of the damaged organ.
• Focal infection. One of the reasons for low-grade fever is the presence of a permanent source of infection in the patient’s body (sinusitis, adnexitis, tonsillitis and others), although in most cases these diseases are not accompanied by high temperatures. The involvement of this pathology in the phenomenon under consideration can only be proven in a practical way: by sanitizing the affected area, we get a decrease in temperature.
• Chronic toxoplasmosis. About 90% of patients suffering from this disease have the symptom we are considering in their symptom set.
• Chronic brucellosis shows a similar picture.
• Low-grade fever is a constant companion to such a disease as acute rheumatic fever.
• The symptom in question may be a consequence of a past infectious disease; doctors call it a “temperature tail.” An example is whooping cough. After the patient ceases to be infectious, his subcortex continues to send signals to cough, and a similar mechanism is triggered here. This results in the so-called post-viral asthenia syndrome - a developing psychopathological disorder. In such a situation, tests show the norm, and the temperature returns to normal on its own, sometimes within a couple of months, and sometimes this can last up to six months. Although this cannot be stated unequivocally. It all depends on the specific disease and the severity of its manifestation.

Non-infectious diseases that can cause long-term low-grade fever include:

• Thyrotoxicosis is a disease of a somatic nature. Its appearance is caused by a high concentration of thyroid hormones in the patient’s blood plasma.
• For some people, low-grade fever is an individual physiological norm.
• The cause of the symptom in question may be physical activity, for example, intense sports.
• A high temperature can appear against the background of emotional overload.
• Due to its individual characteristics, the body is able to respond to food intake with such symptoms.
• Prolonged stay in a hot and stuffy room can provoke a rise in temperature.
• This symptom can cause pregnancy. This is a rare manifestation, but it can appear during the first three to four months from the moment of conception.
• The premenstrual period for some representatives of the fairer sex.
• As long-term medical monitoring shows, when measuring body temperature in different armpits, the measurement results may differ by 0.1-0.3 ˚C. For some reason, the left side shows higher indicators.
• Due to the individuality of the body, a thermometer can record constant high temperatures as a reflex reaction of the body to the measurement procedure itself. This applies only to axillary indicators. When measuring this indicator in the oral cavity and through the anus, no such deviations were detected.

The symptom we are interested in can be provoked by reasons related to the psycho-vegetative area of ​​the human body:

• Autonomic neurosis is a disease associated with organic changes in the tissues of the autonomic nervous system, the result of which is a disruption of their normal functioning.
• Thermoneurosis is an increase in body temperature, the etiology of which is the neurasthenic nature of the pathology. High rates of this disease can last for more than one year.
• The patient has a history of traumatic brain injury.
• Disturbance of structural and functional homeostasis, metabolism and functions in a pathological process affecting the endocrine system.
• Psycho-emotional overload.
• Seasonal or permanent allergization.

Causes of constant low-grade fever

The constant presence of elevated temperature indicators of the human body in the intervals above 37.0 ° C to 38.0 ° C is recorded for a long time: from a couple of weeks to several months, or even more than one year, such a clinical picture falls under the diagnosis of low-grade fever. To deal with a problem, you need to know its source. The causes of constant low-grade fever are somewhat diverse, and the effectiveness of combating this pathology depends on whether the original source is established or not.

The problem in determining the functional causes of low-grade fever is that most patients have a history of a focus of chronic infection.

Causes of low-grade fever in a teenager

Mostly recorded causes of low-grade fever in a teenager are akin to the sources listed above. The most common source of a disease that can provoke high temperatures observed for a long time is an infectious lesion (of various etiologies) of the patient’s body. It would seem that the familiar acute respiratory viral infection (ARVI) in most cases, in addition to general weakness, headache, painful symptoms in the joints, rhinitis and cough, is also accompanied by low-grade fever.

Some infectious diseases (for example, chicken pox, rubella) in infancy pass with virtually no fever or it takes on slightly elevated values, while in adolescence these pathologies are more complicated, and body temperature indicators are fixed at higher numbers.

In the case of a prolonged course of the inflammatory process, the main symptoms often lose their severity and become familiar. The only criterion indicating the presence of an internal problem is low-grade fever that does not go away for a long time. In this situation, determining the root cause of the pathology can be quite difficult.

Foci of infectious damage to a teenager’s body can be:

• Diseases of ENT organs, such as:
  • Sinusitis.
  • Pharyngitis.
  • Rhinitis.
  • Tonsillitis.
  • Laryngitis.
  • Otitis.
  • And other diseases.
• Dental caries or periodontitis.
• Pathological lesions of the digestive tract:
  • Colitis (inflammatory process of the intestinal mucosa).
  • Cholecystitis (inflammatory disease of the gallbladder).
  • Gastritis (inflammation of the mucous membrane of the stomach wall).
  • Pancreatitis (inflammation of the pancreas).
  • Duodenitis (inflammation of the duodenum).
  • And others.
• Infectious and inflammatory lesions of the urinary tract:
  • Cystitis.
  • Urethritis.
  • Pyelonephritis.
  • Other diseases affecting this system.
• Inflammatory diseases affecting the genital organs of a teenager.
• Abscesses formed at injection sites.
• Pathological changes of endocrine genesis.

To make a correct diagnosis and find the cause of low-grade fever, the attending doctor usually prescribes a general blood and urine test for the patient. The result of their study clearly shows the presence or absence of an inflammatory process in the teenager’s body. This conclusion is made on the basis of the leukocyte formula, as well as the level of ESR (erythrocyte sedimentation rate).

Consultations with more specialized specialists are prescribed: dentist, gynecologist, gastroenterologist, otolaryngologist, surgeon, and, if necessary, a neurologist.

To confirm or refute your suspicions, the specialist prescribes an additional examination. This may be ultrasound, computed tomography, radiography and other diagnostic techniques.

If the disease is diagnosed, it is necessary to undergo full drug therapy. Chronic infectious lesions are especially difficult to treat.

Quite rare, but the cause of low-grade fever can be:

Causes of low-grade fever in the evening

Quite often, people accidentally find out that they have a low-grade fever; this is due to the fact that very often such a temperature abnormality does not manifest itself with accompanying pathological symptoms. But before you panic, you should strictly follow the instructions for correctly measuring your temperature. You need to know that measurements in the armpit must be carried out by holding the thermometer for 5 to 10 minutes. When measuring temperature indicators with more modern electronic devices, you must first carefully read the instructions supplied with the device and follow all its requirements. Mostly the measurement time period is also 5 – 10 minutes.

The end of the measurement time should be determined by a sound signal only when the measurement is carried out through the anus. We should just not forget that the temperature measured in the rectum is slightly higher than with a similar measurement in the armpit.

It is worth knowing that the reasons for low-grade fever in the evening can be very commonplace. The human body is organized in such a way that in the interval from four to six o’clock in the morning and from four to eight o’clock in the evening, a physiologically justified increase in body temperature readings can be observed. For many people, such increases fall precisely into the subfebrile zone. To determine that such a picture is an individual feature of your body, you should simply take fixed measurements every three to four hours during the daytime, as well as at least once during the night. It is necessary to carry out such manipulations over several weeks. Summarize the results obtained in a table, this will make it easier to analyze the measurement results.

It is almost impossible to determine the cause of a pathological symptom on your own. And if the measurement reveals low-grade fever, you should seek advice from your local doctor. He is professionally able to assess the situation and, if necessary, write a referral for consultation with a more specialized specialist. At the same time, medical statistics show that for 2% of the world's population, constant low-grade fever, especially in the evening, is the norm.

We should not forget the fact that when measuring body temperature under different armpits, the measurement results in most cases differ by 0.1-0.3 ˚C. The left side generally gives better results.

But the cause of increased thermometer readings in the evening can be an untreated infection, a sluggish inflammatory process that has become chronic, stressful situations, as well as other pathological disorders. But only a qualified specialist can establish the cause and source of the disease. He is also able to describe effective remedial therapy or, if the cause is not related to pathologies, will give the necessary recommendations.

If a person is not in pain, and the thermometer shows a slightly elevated temperature, many people do not attach much importance to such a picture. But after reading this article, we can conclude that ignoring these symptoms can lead to irreversible pathological changes in the human body, because the causes of low-grade fever are quite diverse and the source of the symptom in question can be a fairly serious disease. No one in this article calls for you to immediately panic, but undergoing a full examination, nevertheless, will not be superfluous. After all, the earlier the disease is diagnosed and treated, the greater the likelihood of a favorable outcome, and the likelihood of various complications occurring is minimized.

Low-grade body temperature is understood to mean its fluctuations from 37 to 38 0 C. Long-term low-grade fever occupies a special place in therapeutic practice. Patients whose long-term low-grade fever is the dominant complaint are encountered quite often at appointments. To find out the cause of low-grade fever, such patients are subjected to various studies, they are given various diagnoses and (often unnecessary) treatment is prescribed.
In 70-80% of cases, prolonged low-grade fever occurs in young women with symptoms of asthenia. This is explained by the physiological characteristics of the female body, the ease of infection of the urogenital system, as well as the high frequency of psycho-vegetative disorders.

It must be taken into account that prolonged low-grade fever is much less likely to be a manifestation of any organic disease, in contrast to prolonged fever with a temperature above 38 0 C. In most cases, prolonged low-grade fever reflects banal autonomic dysfunction.

Conventionally, the causes of prolonged low-grade fever can be divided into two large groups: infectious and non-infectious.

Infectious low-grade fever

Low-grade fever always raises suspicion of an infectious disease.
Tuberculosis. If you have an unclear low-grade fever, you must first rule out tuberculosis. In most cases this is not easy to do. From the anamnesis the following are essential:

• Having direct and prolonged contact with a patient with any form of tuberculosis. The most significant is being in the same place with a patient with an open form of tuberculosis: an office, apartment, stairwell or entrance of the house where the patient with bacterial excretion lives, as well as a group of nearby houses united by a common yard.
• A history of previous tuberculosis (regardless of location) or the presence of residual changes in the lungs (presumably of tuberculosis etiology), previously detected during preventive fluorography.
• Any disease with ineffective treatment within the last three months.

Complaints (symptoms) suspicious for tuberculosis include:

• The presence of general intoxication syndrome - prolonged low-grade fever, general unmotivated weakness, fatigue, sweating, loss of appetite, weight loss.
• If pulmonary tuberculosis is suspected, chronic cough (lasting more than 3 weeks), hemoptysis, shortness of breath, chest pain.
• If extrapulmonary tuberculosis is suspected, complaints of impaired function of the affected organ, without signs of recovery against the background of nonspecific therapy.

Focal infection. Many authors believe that prolonged low-grade fever may be due to the existence of chronic foci of infection. However, in most cases, chronic foci of infection (dental granuloma, sinusitis, tonsillitis, cholecystitis, prostatitis, adnexitis, etc.), as a rule, are not accompanied by an increase in temperature and do not cause changes in the peripheral blood. It is possible to prove the causal role of a focus of chronic infection only in the case when sanitation of the focus (for example, tonsillectomy) leads to the rapid disappearance of a previously existing low-grade fever.
A constant sign of chronic toxoplasmosis in 90% of patients is low-grade fever. In chronic brucellosis, the predominant type of fever is also low-grade fever.
Acute rheumatic fever (a systemic inflammatory disease of connective tissue involving the heart and joints in the pathological process, caused by beta-hemolytic streptococcus of group A and occurring in genetically predisposed people) often occurs only with low-grade body temperature (especially in the second degree of activity of the rheumatic process).
Low-grade fever may appear after an infectious disease (“fever tail”), as a reflection of post-viral asthenia syndrome. In this case, low-grade fever is benign in nature, is not accompanied by changes in tests and usually goes away on its own within 2 months (sometimes the “temperature tail” can last up to 6 months). But in the case of typhoid fever, prolonged low-grade fever that occurs after a decrease in high body temperature is a sign of incomplete recovery and is accompanied by persistent adynamia, undiminished hepato-splenomegaly and persistent aneosinophilia.

Non-infectious low-grade fever

Prolonged low-grade fever of a non-infectious nature can be caused by somatic pathology, but much more often it can be explained by physiological reasons or the presence of psycho-vegetative disorders.
Among somatic pathologies, it is worth paying attention to iron deficiency anemia, which can occur with low-grade fever, and thyrotoxicosis.
Thyrotoxicosis. Low-grade fever is almost the rule in case of excess thyroid hormones in the blood. In addition to low-grade fever, thyrotoxicosis most often causes nervousness and emotional lability, sweating and palpitations, increased fatigue and weakness, weight loss against the background of normal or even increased appetite. To diagnose thyrotoxicosis, it is enough to determine the level of thyroid-stimulating hormone in the blood. A decrease in the level of thyroid-stimulating hormone is the first manifestation of excess thyroid hormones in the body.
Physiological reasons. For many people, low-grade fever is constitutional in nature and is a variant of the individual norm. Low-grade fever can develop against the background of emotional and physical (sports) stress, appear after eating, when in a hot room, after exposure to insolation. Women may have low-grade fever in the second half of the menstrual cycle, which normalizes with the onset of menstruation; Rarely, low-grade fever is observed during the first 3-4 months of pregnancy.
In addition, the temperature may not be the same in the left and right armpits (usually the left is 0.1-0.3 0 C higher). A reflex increase in temperature in response to the measurement procedure itself is possible: in such patients, subfebrile temperature is observed only when it is measured in the armpits, and in the rectum or oral cavity the indicators are normal.
It is necessary to know about the physiological causes of fever in order not to expose people in these cases to unnecessary examination and treatment.
Psycho-vegetative reasons. Prolonged low-grade fever in 33% of patients is psycho-vegetative in nature [Vein A.M. et al., 1981] and is considered as a manifestation of the syndrome of vegetative dystonia (vegetoneurosis, thermoneurosis). Periods of low-grade fever in such patients can last for several years. A favorable background for the appearance of psychogenic low-grade fever, in addition to psycho-emotional stress, is allergization, endocrine dysregulation, and a history of traumatic brain injury.
Prolonged low-grade fever is more common in young women with symptoms of asthenia, children in puberty and first-year students.
The diagnosis of “thermoneurosis” should be made only after excluding pathological conditions that can cause low-grade fever (infectious, tumor, endocrine, immunological and other processes).
Low-grade fever during thermoneurosis either monotonically remains at the same level throughout the day, or has a perverted character (morning temperature is higher than evening temperature). Although some patients complain of general malaise, in general they tolerate low-grade fever satisfactorily, maintaining motor and intellectual activity.
Antipyretic drugs have almost no effect on low-grade fever in thermoneurosis, but a good effect has been noted when treated with sedatives. However, in the majority of such patients, even without treatment, low-grade fever can normalize in the summer or during the rest period (regardless of the time of year).

Diagnostics

Finding the causes of prolonged low-grade fever presents certain difficulties and requires a step-by-step approach. Diagnosis should begin with clarification of the epidemiological history and previous diseases, physical examination, and the use of standard and special laboratory and instrumental methods for diagnosing pathological conditions leading to an increase in body temperature. First of all, chronic infections, tumor, endocrine and systemic connective tissue diseases, demyenilizing processes, etc. should be excluded.
Low-grade fever of infectious origin has its own distinctive features from non-infectious low-grade fever (Table 1).

Table 1

We can suggest the following initial plan for examining a patient with prolonged low-grade fever:

1. Fractional temperature measurement in the rectum (preferred) or oral cavity and paracetamol test.
2. Detailed general blood test.
3. General urine analysis, urine analysis according to Nechiporenko.
4. Biochemical blood test: protein fractions, AST, ALT, CRP, fibrinogen.
5. Mantoux, Wasserman reaction, blood test for HIV and viral hepatitis.
6. Assessment of thyroid-stimulating hormone (TSH) levels.
7. X-ray of the chest organs.
8. Electrocardiogram.
9. Gynecological examination (for women).
10. Dentist consultation: examination of the oral cavity, x-ray of the roots of the teeth (if there are crowns).
11. Consultation with an ENT doctor: examination of the tonsils, including culture; Ultrasound or x-ray of the paranasal sinuses.

The second stage of diagnosis, depending on the formed diagnostic hypothesis, includes:

• Analysis of sputum (if any), feces for worm eggs.
• Echocardiography (EchoCG), ultrasound of the abdominal and pelvic organs.
• Blood culture for sterility.
• Duodenal intubation with bile culture.
• Fibrogastroduodenoscopy (FGDS) in people over 45 years of age.
• Blood test for yersiniosis, toxoplasmosis, borreliosis, analysis of a thick drop of blood for malaria, Wright and Heddelson, Vidal reactions, Burnet test.
• Puncture of found space-occupying lesions and aspiration of material for cytological examination (for example, an enlarged lymph node); bone marrow biopsy.
• Consultations with a cardiologist, phthisiatrician, infectious disease specialist, endocrinologist, hematologist, oncologist.

Treatment

If the study reveals that low-grade fever acts as a secondary symptom, then therapeutic efforts are directed toward treating the primary disease.

Non-infectious low-grade fever, which has its own significance, is a reflection of the syndrome of vegetative dystonia (thermoneurosis). Therefore, psychotherapy and the use of sedatives in such patients is pathogenetically justified. To reduce adrenergic activation, beta blockers may be prescribed. An important role is played by the normalization of work and rest, personal relationships and sexual life. Tempering procedures, bathhouse, sauna are shown. Regular physical training is required. It is advisable to undergo sanatorium treatment using balneotherapy, hydrotherapy, and adaptive physiotherapy.

The true causes of low-grade fever are masked by one symptom. This alarms and frightens patients, forcing them to seek medical help. Is this always necessary? Low-grade body temperature and what it is, when it occurs and whether it requires treatment, we will tell you in the article.

Basic clinical terms

Low-grade fever is a symptom due to a nonspecific adaptive reaction of the body in response to aggressive factors of the external and internal environment. The mechanism of occurrence is the effect on the hypothalamic thermoregulation centers.

In clinical practice, a low-grade fever is considered to be a fever of up to 38 °C.

There are classifications to quickly guide a doctor in a situation:

By numerical parameters

• low subfebrile condition – up to 37.5 ˚С;
• high subfebrile condition when the numbers are in the range of 37.6-38 ˚С.

By duration of fever

• short-term (duration up to 5 days);
• long-term (6-15 days);
• prolonged – from 15 days.

Constant low-grade fever with a long course is a consequence of pathology. In such cases, contacting is mandatory!

Why might this occur?

Low-grade fever in a teenager of a short-term nature without affecting general well-being is a variant of the norm due to hormonal changes in combination with psycho-emotional stress. The figure does not exceed 37.5˚С.

Elizarova A.A., pediatrician, Kaluga

Parents also often come to the clinic with prolonged fever in their children.

Finding out the cause sometimes takes a lot of time. Treatment of low-grade fever is not required for this period!

It is selected taking into account the disease that resulted in fever.

Low-grade fever after ARVI occurs due to 2 factors:

• addition of a secondary infection;
• hyperthermic syndrome (more often in young children when thermoregulation processes are disrupted).

The occurrence of such a situation requires seeking medical help for!

Low-grade fever is often detected in women against the background of inflammatory processes of the genital organs and menopause. In this case, the treatment is carried out by a gynecologist, identifying the cause of the problem.

The collected epidemiological history is an important part of the diagnostic process. It is necessary when a low-grade fever is detected in an adult traveling to other countries. This allows you to prescribe the correct examination.

The most unfavorable type of fever is when there is a low-grade fever for a long time. This always indicates pathology. Do not delay your visit to the doctor so as not to miss a dangerous disease.

From laboratory tests, when there is a long-term low-grade fever, the following must be prescribed:

• general blood test (deciphering the general blood test);
• screening for malaria, typhus and tuberculosis;
• chest x-ray;
• Ultrasound of the heart;
• blood test for sterility 3 times!

Subsequently, the examination is prescribed taking into account the results obtained.

Is it necessary to treat

Low-grade fever is a condition that does not require emergency treatment.

In cases where it was a consequence of physiological reasons, Taking antipyretic anti-inflammatory drugs is not contraindicated(Nurofen, Nimulid, Aspirin) and an active drinking regime (hot tea, rosehip decoction, chamomile).

Nurofen is given to children in syrup, at a dose of 5-10 ml per 1 kg of child’s body weight

In other cases, a preliminary diagnostic study is necessary.

An exception is post-vaccination fever in a child. In such cases, 2 medications are indicated:

• anti-inflammatory (Nurofen, Panadol);
• (Fenistil, Zodak, Zyrtec).

This is caused by a special allergic reaction to the vaccine.

Low-grade fever itself does not require treatment. She is a symptom, but not a disease!

Conclusions

The causes of low-grade fever in adults and children are similar. Short-term fever without affecting general well-being does not require emergency treatment. However, it is worth telling your doctor about such episodes to avoid unwanted consequences.

What does low-grade fever mean? The Latin prefix sub means “under, about” (think of words like submarine, offal or subtropics). And febris means “fever” in Latin. So, literally, low-grade fever is defined as “near-febrile.”

Human body temperature is a complex indicator of the thermal, that is, thermal state of the body. The mechanism of our thermoregulation is “automatically” set to the normal value of +36.6°C and allows its physiological changes within the range of plus or minus 0.5-1°C. In this case, the general temperature range is 36-39°C. When the thermometer rises to +38-39°C, doctors talk about febrile temperature, and above +39°C - about pyretic temperature. What is a low-grade fever?

Classic low-grade body temperature is +37-37.5°C, but experts indicate a higher figure - 37.5-38°C. So, quite reasonably, a low-grade temperature of 37 degrees and up to +38°C is considered by most domestic doctors to be “near-febrile”, while their Western colleagues consider a temperature of 99.5-100.9°F or 37.5-38.3°C to be such.

Causes of low-grade fever

The causes of low-grade fever, as well as febrile and pyretic, are associated with changes in the functioning of the limbic-hypothalamoreticular system of the body. Simply put, temperature is regulated in the hypothalamus, which acts as a thermostat. Endogenous or exogenous pyrogens cause the release of prostaglandins (inflammatory mediators), and they act on the neurons responsible for thermoregulation, which are located in the hypothalamus. And the hypothalamus generates a systemic response, and as a result, the body is set to a new temperature level.

Signs of low-grade fever

Low-grade body temperature accompanies a number of diseases, sometimes being, in fact, their only symptom, recorded at the initial stage of development. Apart from elevated temperature, this condition may not manifest itself with any other signs, which poses a potential threat to health.

So the key signs of low-grade fever are a periodic or permanent (constant), short-term or long-term increase in temperature to +37-38°C.

Low-grade fever as a symptom

Low-grade fever is a sign of one or another pathology. Low-grade fever and cough, low-grade fever and headache, as well as weakness and low-grade fever are typical symptoms not only of ARVI or influenza, but also of focal pneumonia and pulmonary tuberculosis. In particular, with focal or infiltrative tuberculosis, low-grade fever is observed in the evenings, which rises for 3-4 hours to +37.3-37.5°C.

Often, low-grade fever after acute respiratory viral infection is the result of incomplete recovery, weakened immunity, or the effects of medications.

In most cases, low-grade fever during bronchitis will not rise above +37.7°C; low-grade fever after pneumonia remains in approximately the same range. Often doctors cannot determine the exact cause of this phenomenon and call it post-infectious low-grade fever.

The characteristic low-grade temperature for tonsillitis is 37-37.5°C, and the low-grade temperature after a sore throat can remain at the same level for one to two weeks. A longer low-grade fever should be alarming, because, as is known, tonsillitis quickly becomes chronic decompensated, and streptococcal infection with frequent sore throats has a pathological effect by intoxicating heart tissue, causing infective endocarditis, and affecting the kidneys, leading to glomerulonephritis.

Low-grade fever with cystitis, along with other symptoms of this disease, goes away after appropriate drug therapy. However, when the low-grade fever remains at 37.5-37.8°C after the end of treatment, then there is good reason to assume that inflammation from the bladder has spread to the kidneys and threatens pyelonephritis.

Low-grade fever after tooth extraction, as well as low-grade fever after surgery performed on any tissues and organs, may have a separate list of reasons, among which in the first place is the body’s reaction to a damaging factor and infection (for example, infectious blood poisoning - pyaemia). Medicines taken both before and after surgery also contribute.

Low-grade fever in oncology is most often observed with myelo- and lymphocytic leukemia, lymphomas, lymphosarcoma and kidney cancer. As oncologists note, prolonged low-grade fever - for six months or even more - is one of the symptoms of the early stages of these diseases. Also, cancer patients after radiation and chemotherapy are characterized by neutropenic low-grade fever associated with a weakened immune system.

Nausea and subfebrile temperature of the gastroenterologist will suggest intestinal dysbiosis. But low-grade fever at night usually drops to a physiologically normal level or slightly lower, although it can persist, for example, with a latent herpesvirus infection, inflammation of the bile ducts or hepatitis C.

It should be borne in mind that a constant low-grade fever, which remains above normal throughout the day and fluctuates by more than one degree during the day, is a symptom of infective endocarditis. Prolonged low-grade fever, which appears every 24-48 hours, is a typical manifestation of malarial plasmodium.

The human immunodeficiency virus acts slowly, so low-grade fever with HIV, in the absence of other signs in carriers of this infection, is an indicator of a total decrease in protective forces. The next stage may be the defeat of the body by any infection with the development of many immune-mediated diseases.

Low-grade fever with VSD

Thermoregulation of the body - like the activity of all internal organs, secretory glands and blood vessels - is coordinated by the autonomic nervous system, which ensures the stability of the internal environment and the adaptive reactions of the body. Therefore, disturbances in its work can manifest themselves as low-grade fever with VSD, that is, vegetative-vascular dystonia.

In addition to a spontaneous daytime increase in temperature to 37-37.3°C, there may be neurocirculatory disorders such as changes in blood pressure and heart rate, decreased muscle tone, and hyperhidrosis (increased sweating).

Depending on the cause of VDS in clinical medicine, vascular dystonia is distinguished: genetic, infectious-allergic, traumatic and psychogenic.

Until recently, an increase in temperature in such conditions, that is, without an obvious cause, was defined as low-grade fever of unknown etiology. It is now known that there is a violation of the thermoregulation process due to diencephalic syndrome - a congenital or acquired dysfunction of the hypothalamus (our main “thermostat”).

Congenital causes of this pathology include functional somatic disorders such as VSD, and acquired causes include cerebral circulatory disorders in the area of ​​the hypothalamus, traumatic brain injuries, encephalitis, intoxication, etc.

Anemia and low-grade fever

Anemia and low-grade fever are quite closely related to each other at the biochemical level. Iron deficiency anemia leads to a disruption in the production of hemoglobin and a decrease in its content in red blood cells that carry oxygen to the cells. And with a lack of oxygen in all cells of the body and, first of all, the brain, the metabolic process is disrupted. Therefore, in addition to all other signs of iron deficiency in the body, a slight increase in body temperature is quite often observed. Children and adolescents during puberty are most prone to iron deficiency anemia. In addition to low-grade fever, they often develop colds, and their appetite and body weight may decrease.

In addition, poor iron absorption is associated with a lack of vitamin B9 (folic acid) and vitamin B12 (cyanocobalamin), which regulate hemoglobin synthesis in the bone marrow. And such anemia is called pernicious.

Precision anemia and low-grade fever - if not paid attention to - can lead to the development of inflammation and atrophy of the mucous membranes of the gastrointestinal tract.

Low-grade fever in women

Low-grade fever before menstruation in women refers to physiological periodic changes in thermoregulation (within 0.5 degrees) and is associated with an increased intake of estrogen and estradiol and their metabolic products into the blood: hydroxyestrons, etiocholanolone, methoxyestradiol, etc.

Low-grade fever during pregnancy (up to +37.5°C) can be observed in the early stages, in the first 12 weeks, due to an increase in the level of progesterone produced by the corpus luteum of the ovaries and its effect on the hypothalamus. Later, temperatures return to normal.

However, a slight but constant low-grade fever in pregnant women is quite possible when blurred symptoms of so-called TORCH infections appear against the background of a natural decrease in immunity: toxoplasmosis, hepatitis B, varicella-zoster virus, rubella, cytomegalovirus and herpes simplex virus. Since all of these infections can cause congenital pathologies of the fetus, it is important to be vigilant during low-grade fever and take a blood test for TORCH infections.

And finally, low-grade fever in women very often occurs during menopause, and this is again due to changes in their hormonal levels.

Low-grade fever in a child

Thermoregulation disorders detected in childhood in at least 2% of cases represent congenital diencephalic syndrome, that is, problems with the hypothalamus, which were discussed above.

Low-grade fever in a child often accompanies infections of the upper respiratory tract, nasopharynx and ears. Thus, low-grade fever and cough can occur with ARVI, chronic tonsillitis, bronchitis, and pneumonia. Temperature is given by teething and vaccinations. Low-grade fever can be provoked by physical activity, severe anxiety, overheating when wearing heavy clothing, anemia, etc.

Low-grade fever in a teenager is associated with the period of puberty, but possible pathologies cannot be ignored. In addition to those listed above (see section Causes of low-grade fever), pediatricians pay special attention to childhood and adolescent thermoneurosis, which is caused by diencephalic syndrome, malignant blood diseases, thyroid pathologies, as well as autoimmune diseases. For example, children under 16 years of age may develop Still's disease or systemic juvenile idiopathic arthritis, which is characterized by weakness and low-grade fever.

It can also be a side effect of long-term use of certain medications, such as atropine, diuretics, anticonvulsants, antipsychotics and antibacterials. Thus, low-grade fever with antibiotics occurs due to the fact that their use erases the signs of certain diseases, and then only one symptom remains - an increase in thermometer readings.

The temperature of the human body is a variable value. It strongly depends on the time of day, being lower at 5-6 am and increasing to maximum values ​​at 18:00. In children, the temperature corresponds to higher values, dropping to 36.6 degrees only at the age of 5 years. In old age, temperature indicators correspond to 36.2-36.5 degrees. What can a low-grade fever indicate?

There are also differences in temperature between women and men, which are determined by their hormonal levels. Recently, the presence of prolonged low-grade fever (more than 2 weeks) has increased in people of all ages. Moreover, in women this symptom is observed three times more often, unlike in men. It is most common among young women aged 20-40 years.

Any effect on the body of viruses, pathogens, allergens, bacteria causes an increase in temperature. During some diseases, hyperthermia takes on high levels, in other cases there is a low-grade fever, which is 37-38 degrees.

The causes of low-grade fever in adults and children can be the following pathological conditions:

• chronic and acute inflammatory diseases;
• infectious processes;
• allergic reactions;
• tumors;
• autoimmune conditions;
• helminthic infections;
• surgical interventions and injuries;
• vegetative-vascular dystonia;
• endocrine disease;
• diseases of the nervous system.

Infectious diseases

Among infectious diseases, low-grade fever in adults most often occurs for acute respiratory diseases which are caused by parainfluenza viruses, influenza viruses, bacteria, adenovirus or rhinovirus. In some cases, low-grade fever after acute respiratory viral infection can last for several weeks; this characterizes the patient’s weak immunity, the presence of immunodeficiency conditions and severe concomitant illness.

Herpetic infection, which occurs in the form of herpes simplex or herpes zoster, is also accompanied by the appearance of low-grade fever. Preicteric type of viral hepatitis passes as a flu-like illness with an increase in temperature to 37.5 degrees. The condition that HIV causes in the first stages can be expressed only by a slight increase in temperature.

Prolonged hyperthermia characterizes the appearance of tuberculosis of any form, expressed as an increase to 37.4 or fluctuations of several degrees throughout the day.

In infectious mononucleosis, hyperthermia can persist for several months.

Inflammatory diseases

Inflammatory processes are the most common causes of low-grade fever:

• diseases of the ENT organs (pharyngitis, sinusitis, otitis, tonsillitis);
• pathologies of the respiratory system, such as bronchiectasis, pneumonia, bronchitis;
• diseases of the gastrointestinal tract (cholecystitis, hepatitis, hemorrhoids, pancreatitis);
• diseases of the genitourinary system (pyelonephritis, cystitis, adnexitis, urethritis);
• diseases of the oral cavity (complicated caries, stomatitis);
• skin diseases (streptoderma, hidradenitis, boil).

Non-inflammatory process

Bronchial asthma, especially its infectious-allergic stage, also passes with the appearance of low-grade fever. Often the only sign other than malaise and weakness is an increase in temperature during tumor processes. Rheumatoid arthritis, autoimmune hepatitis, systemic lupus erythematosus are also accompanied by these symptoms. Since the signs of these diseases can be quite different, these patients require careful examination. A prolonged increase in temperature should be a reason for this.

In recent years, the presence of helminthic infestations has begun to play a major role in the development of many diseases that occur with skin and dyspeptic manifestations. In addition to various additional symptoms, the persistence of low-grade fever for a long time can also be the cause of helminth activity in the body.

The manifestation of additional symptoms such as skin rashes, constipation, depression, nervousness, and grinding of teeth should alert a person to the presence of these pathogens, especially since this problem is very relevant for children and adolescents.

During vegetative-vascular dystonia the presence of low-grade fever is expressed by a spontaneous increase in temperature to 37.2-37.4 degrees, often accompanied by changes in blood pressure, tingling in the heart area and increased sweating.

Presence of low-grade fever after surgery for several days it is characterized as a variant of the norm and is caused by the activation of the body’s defenses and the presence of a significant wound surface. In cases where hyperthermia lasts for a week or longer, then we can talk about the development of complications in the postoperative period.

Wound infection is the most common cause. Very rarely, infection during surgery or damage to internal organs during surgery can occur. The consequences of significant bleeding that occurred during surgery can also cause prolonged normalization of temperature.

Low-grade fever, which is caused by diseases of the nervous system, can be either of organic origin (arachnoiditis, meningitis) or due to psychoses or neuroses. It is for this reason that prolonged passage of increased temperature is why consultation with a neurologist is indicated.

Causes of low-grade fever in women

In women, low-grade fever is often caused by endocrine diseases. Hyperthyroidism, which is accompanied by increased production of thyroid hormones, leads to the appearance of this symptom. This disease is most common in women, but men suffer from it much less often, which is explained by hormonal levels.

In women, low-grade fever can also be explained by physiological reasons related to the production of hormones. After ovulation an increase in temperature is observed in many women, accompanied by the appearance of some other symptoms, such as malaise, irritability, swelling, and increased appetite. In cases where these symptoms disappear with the onset of the monthly cycle, then there is no reason to worry.

Similar mechanisms for the appearance of low-grade fever are also noted during pregnancy. Since this process is accompanied by a restructuring of the entire body and especially its endocrine system, the occurrence of this symptom is quite logical. During pregnancy, low-grade fever is characterized by its presence in the first trimester. Subsequently, there is a decrease in indicators to normal values.

At later stages, the development of low-grade fever may indicate the presence of a sluggish infection.

Since almost all viral diseases are dangerous both directly for the pregnant woman and for her fetus, in these cases you need to consult a gynecologist and perform all the required examinations.

In women, another reason for the development of low-grade fever is climacteric syndrome, which is associated with a decrease in hormone production and is characterized by various additional symptoms. Moreover, sweating, hot flashes to the body and head, increased blood pressure, excessive emotionality, and palpitations are noted.

Causes of low-grade fever in adolescents

Typically, in adolescents, the presence of high fever is associated with puberty and usually appears in boys. But in addition to this, the following pathological conditions can be the causes of low-grade fever in adolescents:

• thermoneurosis;
• malignant blood diseases;
• autoimmune diseases;
• thyroid diseases.

In adolescents and children, the initial symptom of the appearance leukemia Often there is weakness and an increase in temperature. Since in most cases these symptoms can be explained by more favorable and simpler reasons, the main task of parents is to consult a doctor in a timely manner and perform an examination.

In adolescents, to clarify the diagnosis of thermoneurosis, it is necessary to determine the relationship between increased temperature readings, stress and psycho-emotional trauma of the child. In cases where, after a thorough examination of this patient, no other pathology is found, then organizing the correct daily routine, vitamin therapy, and prescribing sedatives will lead to a positive effect.

Rheumatoid juvenile arthritis and Still's disease Although it occurs in 1 in 100,000 people, adolescents under 18 years of age are at risk of developing such an autoimmune severe disease, which is difficult to treat and little studied. In addition to low-grade fever, and sometimes an increase in temperature to a higher value, the diseases are characterized by skin rashes and the development of polyarthritis.

Examination for low-grade fever

When examining patients regarding low-grade fever, it is necessary to exclude false low-grade fever. It is necessary to take into account incorrect thermometer readings that do not correspond to the standard, the possibility of simulation, and an artificial increase in temperature by a person with hysteria and psychopathy.

When excluded false low-grade fever, then you need to perform a clinical and epidemiological examination of the patient. Due to the large list of causes of low-grade fever, an individual approach is required for each patient. The patient is asked for information about previous illnesses and operations, as well as professional data and living conditions. Be sure to perform a thorough physical examination. Then do standard laboratory tests:

If this examination does not help make a diagnosis, then you need to perform an ultrasound of the pelvic and abdominal organs, donate blood for rheumatoid factor, blood for tumor markers, and probably prescribe more invasive diagnostic procedures (biopsy).

How to treat low-grade fever?

An increase in temperature within the subfebrile range almost does not worsen the patient’s general condition and, accordingly, does not require symptomatic treatment. The temperature decreases during the elimination of the disease or cause that led to this condition. For example, with prostatitis, adnexitis and other foci of chronic infection, antibacterial treatment is required. During neuropsychiatric disorders, antidepressant and sedative drugs are used.

But we must not forget that self-medication (especially with salicylates, hormonal drugs, antibacterial agents, etc.) without determining the cause of low-grade fever is unacceptable, since these drugs can affect the course of the disease, cause harm to the patient, “lubricate” the severity of specific symptoms, and may further aggravate the course of the disease, and also complicate the correct diagnosis.

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