Most fevers are caused by infection or other illness. Fever itself usually causes no harm and helps the body fight infections by stimulating natural defense mechanisms. More to Know Causes In a healthy person, a fever usually isn't a sign of anything serious. Although a high temperature can be frightening, a fever can actually be a good thing when it's in response to an infection or illness. Experts believe turning up the heat makes the body a less comfortable place for germs that cause infections. Treatment Not all fevers need to be treated. High fever, however, can be uncomfortable and worsen problems such as dehydration. An important exception: An infant 3 months or younger with a rectal temperature of 100.4°F (38°C) or higher needs immediate medical care. Call your doctor or take the baby to the emergency department immediately. Even a mild fever can be a sign of a potentially serious infection in very young babies. Keep in Mind Home care (rest, plenty of fluids) often is enough to manage a fever. Acetaminophen or ibuprofen can ease discomfort, but kids or teens should not take aspirin, which has been linked to a rare but serious illness called Reye syndrome. Someone with a fever should stay home from school, work, or childcare until the temperature has been normal for 24 hours without the use of fever-reducing medicines. All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts. Back to Articles Related Articles Fevers Fevers happen when the body's internal "thermostat" raises the body temperature above normal. This is often the body's way of fighting infections. Read More First Aid: Fever Fevers are usually not cause for alarm - they're the body's way of fighting infection. Here's what to do if your child has a fever. Read More Dehydration Sometimes kids lose fluids and salts through fever, diarrhea, vomiting, or sweating. Here are some tips on preventing or treating dehydration. Read More Febrile Seizures Febrile seizures are full-body convulsions caused by high fevers that affect young kids. Although they can be frightening, they usually stop on their own and don't cause any other health problems. Read More Flu Facts Every year from October to May, millions of people across the United States come down with the flu. Get the facts on the flu - including how to feel better if you get it. Read More Flu The flu is a virus that can make you sick for a week or longer. Find out more in this article for kids. Read More What's a Fever? What are fevers? Why do kids get them? Get the facts on temperatures and fevers in this article for kids. Read More Word! Fever You've probably noticed that sometimes when you're sick, you feel really hot one minute and then freezing cold the next. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.