What is a fever?

Fever is the body's normal response to infection and other conditions, both minor and serious. Most fevers help the body fight infection.

The average normal body temperature is98.6F (37C)orally. It can change during the day from a low of97.4F (36.3C) in the morning to a high of99.6F (37.6C) in the late afternoon. Mild elevations ( 99.8F) (37.7C) can be caused by too much clothing, a hot bath, or hot weather.

Fever in a child is present when a child's temperature is 100.4F (38C) or higher measured rectally.

A fever is an elevation in body temperature. Usually a fever is a sign that something unusual is happening in the body. The ability to generate a fever is an important part of the body's defense against infection. Most bacteria and viruses that cause infections in people flourish in a 98.6 °F (normal body temperature) environment. Although a fever signals that a battle might be going on in the body, the fever is fighting for the person, not against. The degree of fever does not necessarily indicate the seriousness of the underlying condition.

A fever is an increase in normal body temperature. Healthy individuals typically have a body temperature of about 98.6 degrees Fahrenheit. The body temperature fluctuates by about one degree throughout the day. However, if a person's body temperature increases more than it normally does throughout the day, he/she has a fever. A person can usually recognize when he/she has a fever because it often causes symptoms, such as chills or sweating.

A fever is considered a sign of an underlying medical problem. Most fevers are caused by infections, such as the flu, pneumonia, or strep throat. Other common causes include extreme sunburn, exposure to hot environments, and certain medications. In rare cases, there may be no known underlying cause.

Fevers are usually not dangerous for adults, unless they are 103 degrees Fahrenheit or higher. For infants and very young children, even a slight increase in body temperature may indicate a serious infection. If a baby younger than 12 months old has a temperature higher than 100 degrees, a healthcare provider should be consulted immediately. Adults and children who have temperatures higher than 102 degrees that are not responding to medications, such as ibuprofen (Motrin®, Advil®), aspirin, or acetaminophen (Tylenol®), should visit their doctors.

Most fevers go away in a few days even without treatment. Additional treatments, such as antibiotics, may be necessary depending on the underlying cause of the fever.

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A fever is merely an abnormal rise in body temperature. Normal body temperature varies throughout the day. Exercise, clothing, stress, and vigorous exercise all cause a rise in body temperature. A fever can also be a symptom of an infection. However, high fever does not necessarily indicate a more serious illness than a mild fever.

Remember that normal body temperature varies from person to person. Although we use 98.6 degrees Fahrenheit as the average body temperature, your "normal" temperature may be slightly higher or lower than that. In general, if your temperature is 100 degrees Fahrenheit or higher, you probably have a fever.

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