What Is Fever?

Fever is a sign that something is wrong in the body, although sometimes a person may be ill without an elevation of temperature. A change from the normal body temperature has been used by doctors for years as a basis for judging whether a person is sick, for diagnosing and treating illness, and for noting the progress of the patient’s recovery from illness. One of the first questions asked when illness occurs will frequently be, “What is the temperature?” It is therefore desirable for every family to own a clinical thermometer and to know how to use and care for it.

Temperature should be taken under the following conditions:

1. Whenever a person complains of feeling ill or shows signs of illness.

2. During illness, once or twice a day, at the same time each day, usually once in the morning and once in the evening, or whenever the doctor orders. (Temperatures may be taken as often as every four hours or only once a week, depending on the condition and age of the patient.)

3. Whenever there is a sudden change in the patient’s condition, such as a chill, restlessness, or pain.

4. Whenever there is headache, pain in the chest or the abdomen, sore throat, chills, vomiting, diarrhea, or skin rash.

The patient should not be awakened to have his temperature taken. For accuracy, there must be a wait of at least 15 minutes between the time a temperature is taken and the time the patient has had a hot or a cold bath or has taken hot or cold food or drink, because temperature in the mouth under these conditions will not be the same as the actual body temperature. With older children, the best time to take a temperature is when they are relatively calm or rested.

Besides knowing how to take a temperature and read a thermometer, you should have some knowledge of how to interpret what you read. In adults, a reading of 100 degrees Fahrenheit (37.8 degrees Centigrade) would be considered a significant indication of fever. With infants, 101 degrees Fahrenheit (38.3 degrees Centigrade) would be considered a significant fever. Everyone has variations in temperature during a 24-hour period, and it is normal for the temperature to go up slightly in the late afternoon and to be lowest in the early morning hours.

Bear in mind that fever itself is not an illness. It is a sign of illness. But it doesn’t have to be the only sign. Someone can be extremely sick without running a fever at all. The absence of fever, when other symptoms of illness are present, also should be reported to your doctor.

Don’t panic if your child has a temperature peak of 103 or 104 degrees Fahrenheit (39.4 to 40.0 degrees Centigrade). The height of the temperature isn’t always a measure of how sick a child is. However, a fever in infants under three months old is unusual. It has more significance than the same temperature in older children and should always be diagnosed by your doctor.

Sometimes a doctor will ignore the fever and concentrate on curing the illness itself. This is because the fever is one of the ways the body fights the illness. It is also a means the doctor can use to measure the course of the illness. But if a high fever is interfering with the sick person’s sleep—or exhausting him—the doctor will probably try to lower it. Suzanne Dandoy, M.D., M.P.H., Assistant Director for Community Health Services, Arizona Department of Health

Illustrations by Phyllis Luch