Infection is a common cause of fever, but other conditions can also bring the heat.
Fever is one of the body's most effective ways of fighting infection.
The average body temperature is 98.6° F (37°C). But "normal" body temperature varies from person to person. It also changes during the day, rising a bit after you eat or exercise. Body temperature is often higher in the afternoon than it is when you wake up in the morning.
Fever means a body temperature of 100.4° F (38°C) or higher. An infection, such as the flu, is the most common cause of fever.
Other conditions can also cause a fever. These include diseases that produce inflammation, such as rheumatoid arthritis, reactions to drugs or vaccines, and even certain types of cancers.
People with a fever may also:
- shiver (chills)
- have a headache
- have achy muscles
- not want to eat
- break out in a rash
- be restless
- feel weak.
A very high fever can cause confusion, extreme sleepiness, irritability, and seizures.
Diagnosing the cause of a fever
To help determine why you have a fever, your doctor will ask you about:
- other symptoms such as coughing, abdominal pain, vomiting, diarrhea, or pain when urinating
- recent surgeries or injuries
- recent vaccinations
- new drugs you may be taking
- recent travel, particularly travel abroad.
Treating a fever
Fever is part of your body's defense against infection-causing germs. By itself, fever is usually harmless, though a high fever can be miserable. These steps may help you feel better:
- Drink plenty of fluids to help cool your body and prevent dehydration.
- Eat light foods that are easy to digest.
- Get plenty of rest.
- Take ibuprofen (Advil, Motrin, or others), naproxen, (Aleve, Naprosyn, or others), acetaminophen (Tylenol, others) or aspirin to help relieve head and body aches and lower your temperature.
- Take a slightly warm, not cool, bath or apply damp washcloths to the forehead and wrists.
- Dress lightly (even if you have chills).
If you have a fever over 104°F (40°C) call your doctor. Call your doctor right away if you have a fever along with any of these symptoms:
- loss of consciousness
- stiff neck
- trouble breathing
- severe pain anywhere in the body
- swelling or inflammation of any part of the body
- vaginal discharge that is discolored or smells bad
- pain when urinating or urine that smells bad