What is fever?

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Fever: Overview

A fever is a high body temperature. It's one way your body fights illness. A temperature of up to 102°F can be helpful, because it helps the body respond to infection. Most healthy people can have a fever as high as 103°F to 104°F for short periods of time without problems. In most cases, a fever means that you have a minor illness.


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 is 98.6°F (37°C) orally. It can change during the day from a low of 97.4°F (36.3°C) in the morning to a high of 99.6°F (37.6°C) in the late afternoon. Mild elevations—( 99.8°F (37.7°C) — 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 100.4°F (38°C) or higher measured rectally.

What is a fever temperature?

A core temperature of 100.4°F or above is considered a fever.

How can you care for yourself when you have a fever?

  • Drink plenty of fluids to prevent dehydration. Choose water and other clear liquids. If you have to limit fluids because of a health problem, talk with your doctor before you increase the amount of fluids you drink.
  • Take an over-the-counter medicine, such as acetaminophen (Tylenol), ibuprofen (Advil, Motrin) or naproxen (Aleve), to relieve your symptoms. Read and follow all instructions on the label. No one younger than 20 should take aspirin. It has been linked to Reye syndrome, a serious illness.
  • Rest, and limit activity.
  • Wear lightweight clothing.
  • Eat mild foods, such as soup.

What can cause a fever?

A fever may be caused by:

  • Infections. This is the most common cause of a fever. Examples of infections that can cause a fever include the flu, a kidney infection, or pneumonia.
  • Some medicines.
  • Severe trauma or injury, such as a heart attack, stroke, heatstroke, or burns.
  • Other medical conditions, such as arthritis and some cancers.

What is a fever?

A fever is a high body temperature. It's one way your body fights being sick. A fever shows that the body is responding to infection or other illnesses, both minor and severe.

A fever is a symptom, not an illness by itself. A fever can be a sign that you are ill, but most fevers are not caused by a serious problem.

You may have a fever with a minor illness, such as a cold. But sometimes a very serious infection may cause little or no fever. It is important to look at other symptoms, other conditions you have, and how you feel in general. In children, notice how they act and see what symptoms they complain of.

Giving a child a sponge bath for a fever

If your child's fever is over 104°F (40°C) , contact your doctor. Before you give a sponge bath to a child who has a fever, give your child an appropriate dose of acetaminophen (Tylenol) or ibuprofen (Advil, Motrin). Do not use ibuprofen if your child is less than 6 months old unless the doctor gave you instructions to use it. Wait 30 minutes then check your child's temperature. See whether the medicine brings the child's fever down.

If your child's fever is still elevated and your child is uncomfortable, you might try a sponge bath.

Follow these steps to give a sponge bath.

  • Use lukewarm water [90 °F (32.2 °C) to 95 °F (35 °C) ].

    Do not use cold water, ice, or rubbing alcohol, which will lower the child's body temperature too quickly.

  • Sponge for 20 to 30 minutes.
  • Stop if the child starts to shiver.

If your child doesn't like the sponge bath or doesn't feel better after the bath, there is no need to give another one.

Fever in children: When to call

Call 911 anytime you think your child may need emergency care. For example, call if:

  • Your child passes out (loses consciousness).
  • Your child has severe trouble breathing.

Call your doctor now or seek immediate medical care if:

  • Your child is younger than 3 months and has a fever of 100.4°F or higher.
  • Your child is 3 months or older and has a fever of 104°F or higher.
  • Your child's fever occurs with any new symptoms, such as trouble breathing, ear pain, stiff neck, or rash.
  • Your child is very sick or has trouble staying awake or being woken up.
  • Your child is not acting normally.

Watch closely for changes in your child's health, and be sure to contact your doctor if:

  • Your child is not getting better as expected.
  • Your child is younger than 3 months and has a fever that has not gone down after 1 day (24 hours).
  • Your child is 3 months or older and has a fever that has not gone down after 2 days (48 hours). Depending on your child's age and symptoms, your doctor may give you different instructions. Follow those instructions.

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The content above contains general health information provided by Healthwise, Incorporated, and reviewed by its medical experts. This content should not replace the advice of your healthcare provider. Not all treatments or services described are offered as services by us. For recommended treatments, please consult your healthcare provider.