What Is Fever?

A fever is a temporary rise in body temperature. It’s not considered an illness on its own, but rather a symptom that can be caused by many different conditions. Elevated body temperature can be a sign that the immune system is working — it’s most likely battling a type of infection or illness.

Fevers usually aren’t a cause for serious concern, and they usually go away when the infection does. But extremely high fevers that won’t go down may need treatment.

There are several ways to measure body temperature, so it’s important to read the instructions that come with the thermometer. First, wash your hands with soap and warm water, and clean the thermometer with rubbing alcohol or soap and lukewarm water. Wait to take your temperature until at least 30 minutes after you eat or drink anything hot or cold.

Oral temperature: Turn on the digital thermometer and place the thermometer tip under your tongue. Close your mouth around the thermometer and keep it in place until the thermometer beeps.

Ear temperature: Turn on the digital thermometer and gently place it into the ear canal as indicated by the instructions. Hold the thermometer tightly in place until you hear the thermometer beep.

Temporal artery temperature: Turn on the digital thermometer and gently sweep it across your forehead or point it at the forehead.

Rectal temperature: To take an infant or a child’s temperature rectally, use a thermometer specially made for that purpose, if possible. Follow the instructions to gently place the thermometer in the baby’s anus, and remove after it beeps.

• Elevated body temperature
• Sweating and chills
• Headache and muscle aches
• Fatigue and weakness
• Loss of appetite
• Dehydration

• Viral infections like the flu or COVID-19
• Bacterial infections such as strep throat and some types of pneumonia
• Urinary tract infections (UTIs)
• Gastrointestinal (GI) infections, such as the stomach flu
• Skin infections, including cellulitis, which is caused when bacteria enter through a break in the skin.

Non-infectious causes of a fever include:

• Heat exhaustion
• Certain inflammatory conditions such as rheumatoid arthritis
• A reaction to a medication or vaccination
• Cancer

Although fevers usually go away within a few days, there are signs that a fever could be more serious.

Adults

• Seizure
• Loss of consciousness
• Confusion
• Trouble breathing
• Severe headache
• Stiff neck
• Severe pain in your belly, back, or sides
• Difficulty waking or extreme sleepiness
• Any other unusual or concerning symptom

Infants and Children

• Crying inconsolably
• Difficult to wake up
• Stiff neck
• Red or purple spots on the skin
• Breathing is difficult and doesn’t improve after the nose is cleared
• Unable to swallow anything or drooling excessively
• Extreme sluggishness or drowsiness
• Pain or tenderness in the abdomen
• Dehydration or decreased urination
• Unusual behavior
• Convulsions or seizures

In case of a seizure, put the child on their side. Do not put anything in their mouth.

Infants younger than 3 months with fever need immediate medical evaluation even if they don't display any other symptoms.

• Stay hydrated. You can get dehydrated more quickly if you’re not drinking fluids while you have a fever. Drink what sounds good to you, but avoid overconsuming caffeine.
• Rest and recover. Get plenty of rest and sleep to help your immune system fight off your illness.
• Cool your fever. Adults and older children can use a cold pack to reduce a fever, though it’s best not to use them on small children and babies, because they may be too cold for their sensitive skin. A cool, wet washcloth or a cool or room-temperature bath or shower can help, too. If cooling-down methods cause chills, don’t continue; it may make you or your child feel worse.
• Warm up if you have the shivers. It may seem counterintuitive, but it’s okay to use a blanket to help with your chills. But experts don’t recommend piling on blankets in an effort to “sweat it out.” That raises the risk of dehydration.

Over-the-counter medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and acetaminophen can lower a fever and help with symptoms like headaches or muscle aches.

Aspirin can also help with fever, but it should not be given to children under 18, because it can cause Reye’s syndrome, a serious and potentially life-threatening condition.

In children, don’t give any medication, even over-the-counter fever reducers, without getting your healthcare provider’s okay first.

For adults and children, follow the dosing instructions on the label. Do not take more than recommended.

Rest and fluids are often enough until the fever breaks, but there are situations when you should contact your healthcare provider.

Adults

Adults with a fever should see a healthcare provider in the following situations:

• The fever lasts several days or keeps coming back.

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• The fever doesn’t respond to fever-reducing medications.
• You’re unable to eat or drink without vomiting.
• You recently traveled to an area where a serious infectious disease such as malaria is common.

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• You take immunosuppressant medications.
• You had a recent tick bite.
• You had a recent hospital stay or a recent surgery or another medical procedure.
• You get infections often.
• You have a serious health condition, such as diabetes, heart disease, cancer, lupus, or sickle cell anemia.
• You’re on chemotherapy and your temperature goes above 100.4 for longer than one hour, or above 101 degrees — even just one time.

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Infants and Children

• Infants up to 3 months with a temperature of 100.4 or higher. Fever in infants younger than 3 months could indicate a serious infection.

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• Children older than 3 months who have a fever of 100.4 or higher for more than three days or who are ill and acting sick by being fussy, clingy, or refusing to drink fluids
• Temperature of 104 or greater or if the fever doesn’t come down with a fever-reducing medicine
• Fever that lasts more than 5 days
• Recurrent fever without any other symptoms for more than 7 days, even if the fevers last only a few hours
• Fever and a chronic medical problem such as heart disease, cancer, lupus, or sickle cell anemia

Fevers are a part of life, but there are ways to reduce your chances of getting an infection or illness that have fever as a symptom.

• Adults and children should stay up-to-date on vaccinations as recommended for infectious diseases, such as influenza and COVID-19.
• Wash your hands frequently, especially before eating, after using the toilet, after spending time in a crowd or around someone who's sick, after petting animals, and during or after travel on public transportation.
• Show children how to wash their hands thoroughly, lathering both the front and back of each hand with soap, and rinsing completely under running water.
• Use hand sanitizer when you don't have access to soap and water.
• Try to avoid touching your nose, mouth, or eyes, especially during cold and flu season.
• Cover your mouth when you cough and your nose when you sneeze. Whenever possible, turn away from others, and cough or sneeze into your elbow.
• Avoid sharing cups, water bottles, and utensils.

• A fever is typically a symptom of an underlying infection or illness and is usually not serious.
• Home remedies, such as good hydration, rest, and over-the-counter medications like ibuprofen or acetaminophen, can help manage a fever.
• In some cases, attention from a healthcare provider or even emergency medical care is necessary.
• Preventive measures like staying up-to-date on vaccinations, washing hands frequently, and avoiding close contact with sick people can reduce the likelihood of fevers caused by infections.