Fever in Infants and Young Children

Fever is the abnormally high body temperature resulting from the body’s response to infections, inflammatory conditions or injuries.  

  • When children have fever, they become irritable and show disinclination to eat and drink properly. Their sleep also may be disturbed.
  • Viral infections such as gastroenteritis and cold are the most common cause of fever in infants and children.
  • Fever is diagnosed from the symptoms and from reading the body temperature with a clinical thermometer. The cause of the fever may be determined by a physical examination or further testing.
  • Drugs such as acetaminophen and ibuprofen may be used to bring down the temperature and reduce the discomfort of the child.

Normal body temperature may vary slightly between individuals. Hence, temperature readings below 100.3° F or 38° C are not considered to be a cause concern, unless the child seems distressed. However, if the body temperature is above 100.4° F or 38° C, it is an abnormal condition requiring medical attention, especially in infants below three months.

Causes and Symptoms

The usual causes of fever in infants are viral infections which cause common cold and gastroenteritis in infants and children. Fever due to viral infections subside on its own as the infection gets resolved, and does not require any treatment other than drugs to reduce the temperature and the discomfort of the child. However, fever resulting from bacterial infections, which occur less frequently, requires antibiotic therapy to overcome the infection and lower the body temperature. Ear infections and respiratory tract infections are usually caused by bacteria. Infections of the kidneys and the bladder also may be bacterial in origin.

Certain bacterial infections in the blood may lead to potentially fatal conditions such as meningitis and a widespread infection called sepsis. The only external symptom of these serious conditions may be fever, but more often than not, the affected children look severely ill, which may indicate the severity of their condition and lead to timely diagnosis. Infections are not the only causes of fever, but other conditions causing fever are not very common. Fever due to such other conditions usually persists for several days, often until the causes are detected and treated appropriately.

When infants and children are vaccinated against certain diseases, fever may appear as a reaction to the vaccine. However, it is normal, and should not be a reason to avoid vaccinations. Giving acetaminophen just before and after the vaccination may help avoid fever and associated discomforts resulting from vaccination. Ibuprofen also may be given to lower high temperature.

When infants have fever, they are generally irritable and do not feed well. Their sleep also may be extremely disturbed, which may add to the irritation. Children who are older may become listless and lose interest in activities and play. Very high temperature may make some children unresponsive and extremely lethargic. However, some children may look and act perfectly normal even when they have high fever. In some cases, the rapidly increasing fever may result in seizures which are referred to as febrile seizures.

Diagnosis and Treatment

Fever in infants can be easily diagnosed, but it may be a challenge to determine the exact cause of the fever. Temperature below 100.3° F or 38° C is considered as low grade fever. If no other symptoms or signs of distress are present, low grade fever is often ignored. If it appears for only a short period of time, no treatment is required. Infants having a temperature above 100.4° F or 38° C need to be examined by a doctor to determine the cause. A description of the infant’s symptoms and a thorough physical examination may help the doctor diagnose the cause and prescribe appropriate treatment. In older children, high fevers, recurring fevers, and fevers accompanied by pain, require medical attention.

Very young infants who develop a fever, especially those below 2 months old, require immediate medical attention. It is more difficult to determine the reason for the fever in them, as other accompanying symptoms are not easy to identify. Due to the immaturity of their immune system, they are also more prone to serious infections, and to developing life threatening conditions such as sepsis and meningitis. Blood tests and urine tests are conducted to detect infections which may be causing the fever. A lumbar puncture or spinal tap may be done to test for meningitis. If the doctor notices any abnormality in breathing, a chest x-ray may be done detect respiratory tract infections.

In older infants and young children with fever, detailed testing is not usually done if the doctor diagnoses it to be viral in origin. However, blood tests and urine tests may be prescribed if the infant appears very ill and the cause cannot be determined by a physical examination. In some cases, a spinal tap also may be performed. When children above 3 years have fever, the doctor may be able to assess other symptoms by observing the behavior of the child. After a thorough physical examination, the doctor may decide if any further testing is required. If the child has very high fever, and the cause cannot be determined by physical examination, the doctor may prescribe blood tests and urine tests.

In most cases, the only treatment required may be lowering the temperature and reducing the physical discomforts. Plenty of water should be given to avoid dehydration.  Acetaminophen is commonly used to bring down the temperature. Ibuprofen also can be used reduce fever as well as discomforts associated with it. Once the child feels better, and becomes willing to eat and drink sufficient amount of fluids, no further treatment may be necessary. A sponge bath with warm water may reduce the body temperature and make the child feel even better.

Aspirin should not be given to children to treat fever as it can cause a serious reaction known as Reye’s syndrome in some children who have fever due to viral infections. A child with fever should not be given a cold bath or sponge bath with cold water. Warm water should be used instead. The practice of rubbing a child with alcohol or the extract of witch hazel is not advisable. They carry the risk of being ingested accidentally. They may release harmful fumes which can irritate the eyes too.

If the fever does not subside in a few days, and the reason for the fever is not known, detailed testing may be required to determine the cause. In rare cases, even after detailed testing, the reason cannot be determined. This condition is referred to as fever of unknown origin. When bacterial infections are detected, appropriate antibiotics are prescribed. When the cause of the fever is something other than infections, appropriate medical and surgical treatment may be required.

Measuring a Child’s Temperature

Temperature in the mouth, armpit, rectum or ear can be measured to determine the extent of fever in infants. Both digital and glass thermometers are widely used to measure the temperature, but thermometers which contain mercury are not advised due to the risk of mercury poisoning in case of breakage.

Temperature in the rectum: This gives the closest reading to internal body temperature and can be considered an accurate measure of fever. A digital or glass thermometer, with the bulb smeared with a lubricant such as petroleum jelly, should be inserted gently into the rectum with the child lying down on its front. At least half inch of the thermometer should be inside the rectum and it should be held in position for about two to three minutes.

Temperature in the mouth: Oral temperature is also accurate measure of fever, but the procedure is difficult in infants and young children. The bulb of the thermometer is placed under the tongue and gently held in place by keeping the mouth closed for about three minutes. Digital or glass thermometers can be used.

Temperature in the ear: A special digital device is required to measure the temperature in the ear. This device measures the infrared radiation emanating from the eardrum. The ear canal is sealed with the tip of the device before it is switched on. A digital reading is displayed on the device. The measurement is accurate, but it is not suitable for measuring fever in infants below three months old.

Temperature in the armpit: The thermometer is placed in the armpit and held in place by keeping the arm close to the body for 4 to 5 minutes. The temperature reading is not as accurate as oral or rectal readings, but the procedure is easier and least invasive. Digital or glass thermometers can be used.

Watch This Video about Fever in Infants and Toddlers

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Yasser Elnahas

MD, PHD, Professor Of CardioVascular Surgery
Dr. Yasser Elnahas, Is an associate Professor of Cardiovascular Surgery. Dr. Elnahas was trained as a fellow At Texas Heart Institute And Mayo Clinic Foundation.Dr. Elnahas is dedicated to educating the general public about different disease conditions and simplifying the medical knowledge in an easy to understand terminology.

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