Given that the prefix sub in Latin means "near, under," and febris translates as "fever", it is easy to guess what it is - low-grade body temperature. This is an overestimated indicator of the thermal state of the body. Further - in more detail about why subfebrile temperature is kept, whether it is necessary to knock it down and what tests are to be passed in order to find out the cause of a state close to febrile.
In the body of every healthy person, “automatic settings” of thermoregulation operate. A normal value is considered to be within 36.6 ° C. Minor physiological changes of 0.5 ° C are allowed, both up and down. If the thermometer rises to 38-39 ° , they speak of febrile temperature, but if it is higher than 39 ° - they say fever.
In the understanding of most people, low-grade body temperature is 37-37.5 ° C, while doctors point to a higher indicator - at 37.5-38 ° C. Domestic doctors do not consider such a thermal regimen of the body feverish. Therefore, at subfebrile temperature, interference is not allowed in order to reduce it.
Main reasons
Any increase in body temperature is a consequence of disturbances in the ongoing limbic-hypothalamic-reticular process. In simple words, the thermal regime is set by the hypothalamus, which works like a thermostat. Exposure to external or internal pyrogens provokes the release of inflammatory mediators, which affect the neurons responsible for thermoregulation. Pyrogens are located in the hypothalamus, which, in turn, responds systemically, setting the body a new level of heat output.
The causes of low-grade fever are various pathologies, infectious diseases. The list of ailments accompanied by this symptom is very extensive, since it includes several groups:
- Infectious diseases - influenza, Epstein-Barr virus, acute respiratory viral infections, tuberculosis, mononucleosis, cytomegalovirus, gastroenterocolitis, Lyme disease, AIDS, syphilis, etc.
- Parasitic pathologies - giardiasis, helminthiasis, leishmaniasis, toxoplasmosis.
- Inflammatory foci in the body - chronic diseases of the upper respiratory tract and nasopharynx, soft tissue damage (furunculosis, abscess), focal pneumonia, pancreatitis, cystitis, pyelonephritis, etc.
- Violations of the thyroid gland - hyper- and hypothyroidism, thyrotoxicosis.
- Autoimmune diseases - rheumatoid arthritis, systemic lupus erythematosus, ankylosing spondylitis, Crohn's disease, congenital pathologies.
In addition, a low-grade fever can occur due to the destruction of red blood cells in stroke, acute heart attack, and compression syndrome. Doctors call this phenomenon hemolysis - it causes tissue necrosis, to which the body responds by increasing heat transfer. The indicator on the thermometer can increase with a strong allergic reaction, regardless of its etiology.
Subfebrile condition as a sign of a cold
Mild fever accompanies a number of diseases that manifest without symptoms. Subfebrile temperature is, in fact, their only sign that occurs at the initial stage of development. In addition to the “near febrile” state, the disease may not express itself in any other way, which is the main reason for the delayed diagnosis.
Regardless of the causes of subfebrile temperature, it is characterized by periodic or constant presence. Sometimes the thermometer can increase for a short time, but more often in patients there is a permanent subfebrile condition in the range of 37-38 ° C.
If we consider a mild fever in a person as a sign of a particular pathology, then if it is present with cough, nasal congestion, headache, you can suspect a cold, SARS, or flu. Prolonged subfebrile condition sometimes indicates focal pneumonia, pulmonary tuberculosis. In a predominant number of cases throughout the day, the patient’s body temperature may be within normal limits, but in the afternoon, toward evening, rises to pre-febrile values. Persistent subfebrile condition, which occurs every 1-2 days, is a typical manifestation of malarial plasmodium.
By the way, elevated temperature is often considered a residual phenomenon of acute respiratory viral infections, post-infectious syndrome. The thermal regime is stabilized, as a rule, after a final recovery, strengthening immunity and drug withdrawal.
Fever with inflammation
With bronchitis, low-grade fever is kept within 37.7 ° C. Approximately to the same level, the thermometer rises in case of pneumonia. A characteristic low-grade fever with tonsillitis is 37-37.5 ° C. For a long enough time, a slight fever can remain after a sore throat. But even with such diseases of the respiratory tract, subfebrile condition lasting more than 10 days should alert. If an infectious-inflammatory pathology acquires a chronic decompensated course with frequent exacerbations, the tissues of the heart and kidneys begin to undergo intoxication, as a result of which infectious endocarditis, glomerulonephritis, and inflammation of the bile ducts can develop.
Against the background of progression of diseases of the genitourinary system, a slight increase in body temperature is a very common symptom. Low-grade fever with cystitis , like its other symptoms, disappears after antibiotic drug treatment. But if the pre-febrile condition does not disappear after a course of therapy, we can make an assumption that the inflammatory process managed to affect the kidneys. It should be borne in mind that stable subfebrile temperature, the values ​​of which do not change throughout the day, refers to the symptoms of infectious endocarditis.
Subfebrile condition can occur after extraction of the molar or any surgical intervention. Among the causes of fever, the leading position belongs to the body's response to a damaging factor or bacterial infection.
Another possible reason for the altered heat index is herpes virus infection or hepatitis C. During the day, body temperature can remain within normal limits, and at night it can rise to 37.2-37.5 ° C.
Incurable diseases
Low-grade fever is one of the symptoms of blood diseases. Most often, this symptom is observed with lymphocytic leukemia, various forms of lymphoma, lymphosarcoma, myelogenous leukemia and kidney tumor. Constant weakness and fever over several months may indicate an early stage of the malignant process. It is worth noting that patients who underwent a course of radio and chemotherapy also have a slight fever for a long period. The reason for this is a weakened immune system.
As you know, the human immunodeficiency virus acts slowly, therefore, an increase in body temperature with diagnosed HIV infection to 37.7-38 ° C can be perceived as an indicator of a general weakening of the body's defenses. For such patients, any infection can bring serious complications or prove fatal.
Vegetative dystonia
Based on the physiological characteristics of our body, it is important to understand that normal thermoregulation requires the full functioning of all internal organs, glands and blood vessels, which are coordinated by the autonomic nervous system. It is she who ensures the constancy of the internal environment and the fitness of the body to the effects of external factors. Even minor disturbances in the functioning of the autonomic system can lead to a subfebrile increase in body temperature.
In vegetative-vascular dystonia, in addition to unjustified temperature jumps, other neurocirculatory disorders (for example, changes in blood pressure, increased or slowed heartbeat), the development of muscle hypotension and excessive sweating are also possible.
Until recently, low-grade fever in medicine remained a symptom of unexplained etiology. Today, it is already known for certain that mild fever can occur due to a malfunction in thermoregulation against the background of congenital or acquired diencephalic syndrome. Depending on the causes of the development of vegetative vascular dystonia, several types of it are distinguished in medicine:
- genetic;
- infectious and allergic;
- traumatic;
- psychogenic.
Anemia
Low hemoglobin and subfebrile thermometer values ​​are in close biochemical relationship with each other. Iron deficiency anemia can lead to a disruption in the production of hemoglobin and a decrease in its concentration in red blood cells that transport oxygen to cells. A lack of oxygen, in turn, causes disturbances in metabolic processes. That is why, in addition to other signs of iron deficiency, subfebrile condition is quite often noted. Those under the age of 18 are most prone to anemia. In parallel with an increase in body temperature, their appetite decreases, and insignificant weight loss occurs.
However, not only iron deficiency can lead to a decrease in hemoglobin in the blood. The cause of oxygen starvation of cells is often anemia caused by a lack of folic acid, cyanocobalamin and other B vitamins. These trace elements are responsible for the synthesis of hemoglobin in the bone marrow. This type of anemia is called precision, and it is also accompanied by a low-grade fever. In the absence of treatment for anemia, it is possible to develop atrophic lesions of the mucous membranes of the digestive tract.
Female subfebrile condition
If none of the above factors is the cause of the patient’s body temperature increase, you should pay attention to her menstrual cycle. The temperature in women to subfebrile values ​​often rises before the approaching “critical days” and is one of the options for the normal course of premenstrual syndrome. It should be noted that periodic and minor changes in thermoregulation should not cause concern. An increase of no more than 0.5 degrees is usually associated with the active production of female hormones and their metabolic products.
In addition, mild fever and hot flashes haunt women during menopause. These changes in well-being are also associated with hormonal changes.
In pregnant women, the cause of subfebrile temperature of not more than 37.5 ° C is an increase in the concentration of progesterone in the blood produced by the corpus luteum of the ovaries, and its effect on the hypothalamus. Such a symptom can occur in the first trimester. At a later date, these indicators stabilize.
If a pregnant woman constantly has low-grade fever, it is necessary to exclude the manifestation of TORCH infections, which include toxoplasmosis, hepatitis B, rubella, cytomegalovirus and herpes. TORCH infections pose a threat to the fetus - it is these diseases that, if the mother gets them during pregnancy, can lead to the development of congenital pathologies. If the infection was present in the woman’s body at the time of conception, its activation against the background of weakened immunity cannot be ruled out. Therefore, pregnant women need to be vigilant, monitoring their body temperature daily, and in case of persistent subfebrile condition, undergo an appropriate examination.
Why occurs in childhood
Low-grade fever in a child is most often a symptom of an infection of the upper respiratory tract, nasopharynx and ears. In babies up to two years, the cause of this condition may be teething and routine vaccination. According to many pediatricians, unstable thermoregulation in children under five years of age should not cause special feelings if it is not accompanied by any additional symptoms, since at an early age an increase in indicators is easily provoked by physical activity, overheating, and hypothermia. Much less often, low-grade fever in a child causes diencephalic syndrome - a congenital disorder of the hypothalamus.
The reason for the change in thermoregulation in the adolescent period is considered to be hormonal imbalance that arose during puberty. The probability of pathological problems cannot be ignored. In adolescents, subfebrile temperature can be a symptom of blood cancer, thyroid disease, and autoimmune diseases. Children under 16 are at risk for juvenile rheumatoid arthritis and systemic lupus erythematosus - these diseases are difficult to treat and are accompanied by fever.
Can subfebrile temperature be a side effect of long-term medication use? This question is often asked by children's specialists, but it is unlikely that they will be able to answer it unambiguously. Substances of individual medications are really capable of influencing thermoregulation, among them atropine, antibiotics, diuretics, anticonvulsants, antipsychotic drugs. For example, with prolonged antibiotic therapy, the immune system is seriously affected, which is what signals an increase in body temperature. But each organism reacts differently to drugs, so it would be wrong to summarize and state with absolute certainty about the effect of drugs on temperature indicators.
How to correctly measure the temperature in a child
The temperature in children does not need to be measured:
- immediately after waking up;
- after eating;
- after vigorous physical activity;
- during crying, tantrums, in a worried state.
Indicators may be overestimated for natural physiological reasons. During rest, the temperature may drop. A slight lowering of the column on the thermometer is also possible if the child has not eaten for a long time. To measure the temperature, you need to wipe the armpit dry. The thermometer should be tightly clamped and held for at least 10 minutes.
Diagnostics
With a problem such as subfebrile condition, you can contact one of these doctors:
- TB specialist;
- family doctor;
- general doctor;
- infectious disease specialist.
But you need to understand that not one of the experts will be able to say that finding out the cause of subfebrile temperature is the simplest task. Making the correct diagnosis with this symptom will require a comprehensive examination, passing a number of laboratory tests.
At subfebrile temperature, first of all, an assessment of the so-called temperature curve will be required. To compile it, the patient must use the data of temperature measurements, which he takes every day once every 12 hours. For example, at 9.00 in the morning and at 21.00 in the evening. Measurements are carried out for a month, the results will be analyzed by the attending physician. If a specialist is convinced of the persistence of subfebrile condition, the patient will have to consult with specialized doctors:
- otolaryngologist;
- cardiologist;
- TB specialist;
- endocrinologist;
- Dentist
- oncologist.
At subfebrile temperature, the patient must be given a direction for taking a blood test. If all indicators are normal, the examination continues. In addition to the general analysis, the patient will have to undergo a number of other blood tests:
- for sexually transmitted diseases (syphilis, HIV), viral hepatitis B and C;
- on TORCH infections;
- on rheumatoid factor;
- on thyroid hormones;
- on tumor markers.
If these results do not give an answer to the question of interest, you will also have to pass a urinalysis, fecal analysis for helminth eggs and bacteriological culture of sputum for tuberculosis.
Treatment
It is immediately worth noting that it is not necessary to bring down the low-grade fever. If in this situation the doctor prescribes taking antipyretic drugs, it remains only to draw a conclusion about his incompetence. At a low temperature, taking Aspirin, Paracetamol or Ibuprofen tablets is not necessary, despite the fact that subfebrile condition has been observed for a long time.
It is not necessary to bring down subfebrile temperature with drugs. All you need to do in this case is to seek medical advice from a qualified doctor. In the absence of additional symptoms and complaints of worsening well-being, there is no need to treat low-grade fever. Appointment of correct therapy is almost impossible if the etiology of this condition remains unclear.
For prophylaxis
Literally a hundred years ago, subfebrile condition was called “general malaise” and it was advised to treat it with balanced nutrition, good rest, avoiding stress and walking in the fresh air. And no matter how strange it may sound, for many, these recommendations were not worthless.
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- Minimize the use of harmful foods.
- Refuse alcohol and smoking.
- Full rest and observe the daily routine.
- Receive moderate exercise and walk in the fresh air.