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High fever for no apparent reason in a child
Last reviewed: 04.07.2025

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Temperature without a reason in a child can be a normal reaction of the body to environmental conditions, but it can also be a symptom of a disease. Most often, an elevated temperature is the first symptom, so there is no reason for it as such. But it is still important to find the cause of hyperthermia in a child, because sometimes it is an important symptom of a serious pathology.
Epidemiology
Statistics on the prevalence of this problem show that fever in children is the most common complaint when visiting a doctor. In 76% of children, fever is the only symptom, without other visible and obvious causes. According to statistics, the younger the child, the higher the probability of fever due to an infectious agent, be it a viral or bacterial agent. In children, a systematic review showed that infectious disease (37.6%) was the main cause of fever without a cause, followed by malignant tumors (17.2%), various diseases (16.1%), and vascular diseases and collagenoses (14.0%).
Causes of fever without cause in a child
Fever is a common complaint in children. Most fevers are due to self-limited viral infections and require no more than symptomatic treatment. Occasionally, fever is caused by common bacterial infections that are diagnosed by history and physical examination and require antibiotic treatment without laboratory evaluation. In a few clinical situations, the cause of fever is not easily identified. Every child has a fever from time to time, and it is usually nothing to worry about. But it is important to know what to do when it happens.
Fever is a temperature of 37.5º and above. To talk about the causes of increased body temperature, you need to know the pathogenesis of such a process.
The body has several ways to maintain normal temperature. Organs involved in temperature regulation include the brain, skin, muscles, and blood vessels. The body responds to temperature changes in the following ways:
- increase or decrease in sweat production;
- movement of blood away from or closer to the surface of the skin;
- getting rid of excess fluid or retaining it in the body;
- naturally wanting to seek cooler or warmer environments.
Risk factors
Risk factors for increased body temperature due to serious systemic or malignant diseases are higher in families in which such pathology occurs.
Such diseases are among the most serious causes of fever, and therefore the child should be examined very carefully, if, of course, there are grounds for this.
Of the physiological causes of increased body temperature without other manifestations, teething is most common in children in the first year of life. The pathogenesis of the appearance of elevated temperature during teething may be that such a condition in a baby can be caused by a decrease in the body's reactivity. After all, when teeth begin to erupt, the body always perceives this as a stressful situation. Many biologically active substances and vitamins are released for this process, which can slightly cause activation of the thermoregulation center. But such a temperature should not exceed subfebrile numbers, regardless of which tooth is erupting. Parents must take this into account before thinking that a child's temperature is unexplained because of teeth.
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Pathogenesis
The pathogenesis of the process of increasing body temperature itself consists of a series of reactions on the part of the body. Chemical substances called cytokines and mediators are produced in the body in response to the invasion of a microorganism or other intruder.
The body is forced to produce and activate more macrophages in response, which are cells that go into battle. These cells essentially eat the infecting organism. The body actively tries to create natural antibodies that fight the infection. These antibodies will recognize the infection the next time it tries to invade.
Many bacteria are enclosed in a membrane. When this membrane is destroyed, the contents that can come out of the microorganism can be toxic to the body and also increase the production of macrophages. Macrophages, in order to increase the intensity of their work, produce active substances and mediators that enter the brain. The brain has a center for regulating body temperature. These substances act on this center, and thus increase the temperature. All this is a protective reaction, since organisms cannot withstand the increase in temperature and die.
Temperature increases for a number of reasons: infectious diseases, the effects of certain medications, heat stroke, blood transfusion, physiological changes in the body.
A fever in a baby under 3 months of age is unusual and cause for concern. Fevers in babies aged 3 to 6 months have a higher chance of being serious. Most fevers in young children over 6 months of age are not serious, and most fevers are caused by a non-serious viral infection. Many viral infections that affect young children cause a fever that lasts up to 48 hours before other symptoms appear. A small number of common viruses cause fevers that last longer. The actual temperature level in a fever is not a good guide to how sick a baby is when he or she is over 6 months of age. So don't judge how sick a baby is by a low-grade fever that lasts about a week, for example.
A longer increase in temperature without other symptoms and visible causes may indicate a bacterial infection. For such a cause of fever, the onset of the disease is more typical with hyperthermia without other symptoms. A bacterial cause of fever can be of any localization - it can be bacterial pneumonia, meningitis, poliomyelitis.
If we talk about older children, we need to think about systemic diseases with damage to connective tissue. Such diseases often manifest themselves as a prolonged increase in body temperature without other manifestations, and after some time a rash, joint pain and other characteristic symptoms appear.
In children, an increase in temperature without a reason can also occur due to tumor processes, as well as malignant blood diseases.
Symptoms of fever without cause in a child
What are the signs that my child may have a fever? Children with a fever may become more cranky or lethargic as their temperature increases. However, each child may experience symptoms differently. Your child may be less active or talkative than they normally are when they are healthy. They may seem more cranky, have a decreased appetite, or be more thirsty. Your child may feel hot during hyperthermia or cold as their temperature drops. Remember that even if your child feels like they are “burning,” their actual rectal or oral temperature may not be that high.
Cold symptoms may appear after a few days or hours if the cause is a viral infection. Then you will see that the baby has a runny nose, cough, inflammation of the eyelids and other symptoms. Therefore, given that an elevated body temperature without a reason is often accompanied by the further development of symptoms of an infectious lesion, parents need to be alert in this regard.
A child's temperature without cold symptoms often occurs when the infectious lesion is caused by bacteria. In such cases, everything starts with a high body temperature, which can last for a long time, and then a cough appears. This is more typical for bacterial pneumonia.
If there is a high temperature and no cough or other respiratory symptoms, then you need to look for other causes. Sometimes the child himself cannot say what hurts, so you need to ask him if his legs, tummy, or head hurt.
Temperature can have different degrees of increase - from 37 to 40 without reason in a child, regardless of age: from several months to 13 years and older. As a rule, the pattern is traced in the case where, for example, the age of the child is up to one year, and the temperature fluctuates around 37-37.5 degrees, then, most likely, the cause is teething. The higher the temperature in younger children, the more serious the reason for this. As for older children, they can describe their condition in more detail. If there is a temperature, the child can talk about pain in the muscles, joints, as well as other manifestations.
Complications and consequences
The consequences and complications of a fever can be significant. When it comes to infants, some children have a tendency to have febrile seizures. This is a type of adjustment caused by a rapid increase in body temperature. Febrile seizures and seizures due to infections, such as meningitis, can look very similar. If a child has a seizure for the first time, it is important to rule out serious conditions, such as meningitis, before deciding that it is a febrile seizure.
Diagnostics of fever without cause in a child
It is very important in diagnostics to measure body temperature correctly, as well as to control and interpret it. If the mother began to measure the child's body temperature in the armpit area, then further measurements should also be taken in this area. In children, in addition, it is possible to measure in the groin area, in the mouth, on the eardrum or in the rectum. Given the measurement method, different thermometers are used, but you should always remember about hygiene and safety measures.
When a doctor makes a diagnosis, it is important that the doctor confirms the temperature by taking it himself. It is important to pay attention to the signs that usually accompany a fever - for example, tachycardia, chills. It is very important to conduct a thorough interview with the parents. It is necessary to ask about symptoms from all major systems. Include general complaints - for example, fever, weight loss, night sweats, headaches and rash.
Discuss your child's diet, including dairy consumption and the source of these products. After all, infections can be transmitted through food.
Fever without cause and without any other symptoms requires further evaluation, which includes laboratory tests or instrumental studies.
If a child has had a fever for a few days and then everything returns to normal, there is no need to worry too much. This could be a symptom of simple overheating or teething. But if the temperature has been elevated for a long time and no cause can be found, then such a child should be thoroughly examined.
The tests that must be performed are limited to mandatory tests - general urine analysis, blood analysis, biochemical blood analysis, stool analysis. If there are changes in the urine analysis, then a disease of the urinary tract can be diagnosed. In small children who cannot complain of back pain or pain when urinating, such an analysis can be very informative. Moreover, a persistent infection of the kidneys or bladder can cause an increase in temperature without other manifestations.
A general blood test allows us to exclude an infectious process of viral or bacterial etiology as the cause of the temperature. A biochemical analysis allows us to judge the function of the liver and kidneys, the normal functioning of the immune system and also the presence of inflammatory agents.
Instrumental diagnostics can be performed to identify the localization of the process and the cause of fever. Most often, if pneumonia is suspected, an X-ray examination is performed. The most common screening method that can be used for children of different ages is an ultrasound examination. Internal organs are examined - the heart, liver, spleen, abdominal organs, kidneys. This allows you to assess the condition of the internal organs, exclude developmental defects and possible inflammatory and other changes.
Differential diagnosis
Differential diagnosis of fever should be done primarily by parents, and it is necessary to exclude those conditions when the temperature can be a dangerous symptom. All symptoms associated with harmless viral fevers can also occur with more serious diseases. It is difficult to determine whether the child is bothered by fever symptoms or there are other serious diseases. There are some differential signs of elevated temperature that will help you assess whether you need to seek medical help:
- your child is 3-6 months old and has a temperature over 39 C.
- Pale skin, lips or tongue.
- Awakens only with prolonged effort.
- Dry mouth and lips.
- Poor nutrition in infants and decreased urine output in infants.
Such differential diagnostics will help the mother to some extent to determine how severe the fever is and whether it is necessary to see a doctor, and the doctor will then identify the cause.
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Treatment of fever without cause in a child
Treatment of temperature without cause is, first of all, symptomatic therapy - this is the main thing that every mother should remember. It is impossible to immediately give antibiotics or other drugs not prescribed by a doctor at the first or every increase in temperature.
If the baby has a high temperature, it needs to be lowered to safe levels. Temperatures above 38.5 require lowering, and if the temperature is below these numbers, it will lower on its own, you just need to monitor this process.
If you don't have any medications at home, then folk methods can be used as emergency aid for a while. What is allowed to be used in children to reduce the temperature are physical methods.
You can undress the child, uncover, and air the room. If the child has cold hands or feet against the background of a high body temperature, you can rub them with your palms. You can only wipe the child with water at room temperature.
What you should not do with children is wipe them with vinegar, cold water, or wipe them with oils or animal fats, as this can cause additional heating.
Of the medications for treatment in children of any age, only two drugs are allowed - ibuprofen or paracetamol. You can give them alternately, adhering to the time interval. Paracetamol can be given in the form of syrup every four hours. The dosage is 10-15 milligrams per kilogram of body weight. Ibuprofen is dosed at 8-10 milligrams per body weight of the baby. It is important to take the dosage not by age, but by the weight of the child, because the child's weight may not correspond to the age.
Herbal treatment and homeopathic remedies are used in children, but only taking into account the cause of the temperature. If the doctor has determined what exactly caused such an increase in temperature, then various etiopathogenetic methods of treatment can be used.
More information of the treatment
Drugs
Forecast
The prognosis for elevated temperature is usually favorable for recovery if such an increase does not exceed three to five days. In this case, it may be a symptom of a simple viral infection.
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