Fever
Elevated temperature; Hyperthermia; Pyrexia; FebrileFever is the temporary increase in the body's temperature in response to a disease or illness.
A child has a fever when the temperature is at or above one of these levels:
- 100.4°F (38°C) measured in the bottom (rectally)
- 99.5°F (37.5°C) measured in the mouth (orally)
- 99°F (37.2°C) measured under the arm (axillary)
An adult probably has a fever when the temperature is above 99°F to 99.5°F (37.2°C to 37.5°C), depending on the time of day.
Considerations
Normal body temperature may change during any given day. It is usually highest in the evening. Other factors that may affect body temperature are:
- A woman's menstrual cycle. In the second part of this cycle, her temperature may go up by 1 degree Fahrenheit or more.
- Physical activity, strong emotion, eating, heavy clothing, medicines, high room temperature, and high humidity can all increase body temperature.
Fever is an important part of the body's defense against infection. Most bacteria and viruses that cause infections in people thrive best at 98.6°F (37°C). Many infants and children develop high fevers with mild viral illnesses. Although a fever signals that a battle might be going on in the body, the fever is fighting for, not against the person.
Brain damage from a fever generally will not occur unless the fever is over 107.6°F (42°C). Untreated fevers caused by infection will seldom go over 105°F (40.6°C) unless the child is overdressed or in a hot place.
Febrile seizures do occur in some children. Most febrile seizures are over quickly and do not mean your child has epilepsy. These seizures also do not cause any permanent harm.
Febrile seizures
A febrile seizure is a convulsion in a child triggered by a fever.
Read Article Now Book Mark ArticleUnexplained fevers that continue for days or weeks are called fevers of undetermined origin (FUO).
Causes
Almost any infection can cause a fever, including:
- Bone infections (osteomyelitis), appendicitis, skin infections or cellulitis, and meningitis
Osteomyelitis
Osteomyelitis is a bone infection. It is caused by bacteria or other germs.
Read Article Now Book Mark ArticleAppendicitis
Appendicitis is a condition in which your appendix gets inflamed. The appendix is a small pouch attached to the end of the large intestine.
Read Article Now Book Mark ArticleCellulitis
Cellulitis is a common skin infection caused by bacteria. It affects the middle layer of the skin (dermis) and the tissues below. Sometimes, muscle...
Read Article Now Book Mark ArticleMeningitis
Meningitis is an infection of the membranes covering the brain and spinal cord. This covering is called the meninges.
Read Article Now Book Mark Article - Respiratory infections such as colds or flu-like illnesses, sore throats, ear infections, sinus infections, mononucleosis, bronchitis, pneumonia, and tuberculosis
Colds
The common cold most often causes a runny nose, nasal congestion, and sneezing. You may also have a sore throat, cough, headache, or other symptoms....
Read Article Now Book Mark ArticleFlu
The flu (influenza) is a viral respiratory illness that causes fever, chills, runny nose, body aches, and cough. It spreads easily from person to pe...
Read Article Now Book Mark ArticleSore throats
Pharyngitis, or sore throat, is discomfort, pain, or scratchiness in the throat. It often makes it painful to swallow.
Read Article Now Book Mark ArticleEar infections
Otitis is a term for infection or inflammation of the ear.
Read Article Now Book Mark ArticleSinus infections
Sinusitis is present when the tissue lining the sinuses become swollen or inflamed. It occurs as the result of an inflammatory reaction or an infect...
Read Article Now Book Mark ArticleMononucleosis
Mononucleosis, or mono, is a viral infection that causes fever, sore throat, and swollen lymph glands, most often in the neck.
Read Article Now Book Mark ArticleBronchitis
Acute bronchitis is swelling and inflamed tissue in the bronchi, the main passages that carry air to the lungs. This swelling narrows the airways, w...
Read Article Now Book Mark ArticlePneumonia
Pneumonia is a breathing (respiratory) condition in which there is an infection of the lung. This article covers community-acquired pneumonia (CAP). ...
Read Article Now Book Mark ArticleTuberculosis
Pulmonary tuberculosis (TB) is a contagious bacterial infection that involves the lungs. It may spread to other organs.
Read Article Now Book Mark Article - Urinary tract infections
Urinary tract infections
A urinary tract infection, or UTI, is an infection of the urinary tract. The infection can occur at different points in the urinary tract, including...
Read Article Now Book Mark Article - Viral gastroenteritis and bacterial gastroenteritis
Viral gastroenteritis
Viral gastroenteritis is an infection of the stomach and intestine caused by a virus. The infection can lead to diarrhea and vomiting. It is someti...
Read Article Now Book Mark ArticleBacterial gastroenteritis
Bacterial gastroenteritis occurs when there is a bacterial infection of your stomach or intestines.
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Children and adults may have a low-grade fever for 1 or 2 days after some immunizations.
Immunizations
Vaccines are used to boost your immune system and prevent the risk of infection and the severity of infections, including those that cause serious, l...
Read Article Now Book Mark ArticleTeething may cause a slight increase in a child's temperature, but not higher than 100°F (37.8°C).
Teething
Teething is the growth of teeth through the gums in the mouth of infants and young children.
Read Article Now Book Mark ArticleAutoimmune or inflammatory disorders may also cause fevers. Some examples are:
- Arthritis or connective tissue illnesses such as rheumatoid arthritis and systemic lupus erythematosus
Arthritis
Arthritis is inflammation or degeneration of one or more joints. A joint is the area where 2 bones meet. There are more than 100 different types of...
Read Article Now Book Mark ArticleRheumatoid arthritis
Rheumatoid arthritis (RA) is a disease that leads to inflammation of the joints and surrounding tissues. It is a long-term disease. It can also aff...
Read Article Now Book Mark ArticleSystemic lupus erythematosus
Systemic lupus erythematosus (SLE) is an autoimmune disease. In this disease, the immune system of the body mistakenly attacks healthy tissue. It c...
Read Article Now Book Mark Article - Ulcerative colitis and Crohn disease
Ulcerative colitis
Ulcerative colitis is a condition in which the lining of the large intestine (colon) and rectum become inflamed. It is a form of inflammatory bowel ...
Read Article Now Book Mark ArticleCrohn disease
Crohn disease is a disease where parts of the digestive tract become inflamed. It most often involves the lower end of the small intestine and the be...
Read Article Now Book Mark Article - Vasculitis or periarteritis nodosa
Vasculitis
Hypersensitivity vasculitis is an extreme reaction to a drug, infection, or foreign substance. It leads to inflammation and damage to blood vessels,...
Read Article Now Book Mark ArticlePeriarteritis nodosa
Polyarteritis nodosa is a serious inflammatory blood vessel disease. The small and medium-sized arteries become swollen and damaged.
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The first symptom of a cancer may be a fever. This is particularly true of Hodgkin disease, non-Hodgkin lymphoma, and leukemia.
Hodgkin disease
Hodgkin lymphoma is a cancer of lymph tissue. Lymph tissue is found in the lymph nodes, spleen, liver, bone marrow, and other sites.
Read Article Now Book Mark ArticleNon-Hodgkin lymphoma
Non-Hodgkin lymphoma (NHL) is cancer of the lymph tissue. Lymph tissue is found in the lymph nodes, spleen, and other organs of the immune system. W...
Read Article Now Book Mark ArticleLeukemia
Leukemia is a type of blood cancer that begins in the bone marrow. Bone marrow is the soft tissue in the center of the bones, where blood cells are ...
Read Article Now Book Mark ArticleOther possible causes of fever include:
- Blood clots or thrombophlebitis
Blood clots
Blood clots are clumps that occur when blood hardens from a liquid to a solid. A blood clot that forms inside one of your veins or arteries is calle...
Read Article Now Book Mark ArticleThrombophlebitis
Thrombophlebitis is swelling (inflammation) of a vein. A blood clot (thrombus) in the vein is the most common cause of this swelling.
Read Article Now Book Mark Article - Medicines, such as some antibiotics, antihistamines, and seizure medicines
Home Care
A simple cold or other viral infection can sometimes cause a high fever (102°F to 104°F or 38.9°C to 40°C). This does not mean you or your child has a serious problem. Some serious infections don't cause a fever or can cause a very low body temperature, most often in infants.
If the fever is mild and you have no other problems, you do not need treatment. Drink fluids and rest.
The illness is probably not serious if your child:
- Is still interested in playing
- Is eating and drinking well
- Is alert and smiling at you
- Has a normal skin color
- Looks well when their temperature comes down
Take steps to lower a fever if you or your child is uncomfortable, vomiting, dried out (dehydrated), or not sleeping well. Remember, the goal is to lower, not eliminate, the fever.
When trying to lower a fever:
- Do not bundle up someone who has chills.
- Remove excess clothing or blankets. The room should be comfortable, not too hot or cool. Try one layer of lightweight clothing, and one lightweight blanket for sleep. If the room is hot or stuffy, a fan may help.
- A lukewarm bath or sponge bath may help cool someone with a fever. This is effective after medicine is given -- otherwise the temperature might bounce right back up.
- Do not use cold baths, ice, or alcohol rubs. These cool the skin, but often make the situation worse by causing shivering, which raises the core body temperature.
Here are some guidelines for taking medicine to lower a fever:
- Acetaminophen (Tylenol) and ibuprofen (Advil, Motrin) help reduce fever in children and adults. Sometimes health care providers advise you to use both types of medicine.
- Take acetaminophen every 4 to 6 hours. It works by turning down the brain's thermostat.
- Take ibuprofen every 6 to 8 hours. Do not use ibuprofen in children 6 months or younger.
- Aspirin is very effective for treating fever in adults. Do not give aspirin to a child unless your child's provider tells you to.
- Know how much you or your child weighs. Then check the instructions on the package to find the correct dose.
- In children 3 months or younger, call your child's provider first before giving medicines.
Eating and drinking:
- Everyone, particularly children, should drink plenty of fluids. Water, ice pops, soup, and gelatin are all good choices.
- In younger children do not give too much fruit juice or apple juice, and do not give sports drinks.
- Although eating is fine, do not force foods.
When to Contact a Medical Professional
Contact a provider right away if your child:
- Is 3 months or younger and has a rectal temperature of 100.4°F (38°C) or higher
- Is 3 to 12 months old and has a fever of 102.2°F (39°C) or higher
- Is 2 years or younger and has a fever that lasts longer than 24 to 48 hours
- Is older and has a fever for longer than 48 to 72 hours
- Has a fever of 105°F (40.5°C) or higher, unless it comes down readily with treatment and the person is comfortable
- Has other symptoms that suggest an illness may need to be treated, such as a sore throat, earache, or cough
Earache
An earache is a sharp, dull, or burning pain in one or both ears. The pain may last a short time or be ongoing. Related conditions include:Otitis m...
Read Article Now Book Mark ArticleCough
Coughing is an important way to keep your throat and airways clear. But too much coughing may mean you have a disease or disorder. Some coughs are d...
Read Article Now Book Mark Article - Has had fevers come and go for up to a week or more, even if these fevers are not very high
- Has a serious medical illness, such as a heart problem, sickle cell anemia, diabetes, or cystic fibrosis
- Recently had an immunization
- Has a new rash or bruises
- Has pain with urination
- Has a weakened immune system (because of long-term [chronic] steroid therapy, a bone marrow or organ transplant, spleen removal, HIV/AIDS, or cancer treatment)
- Has recently traveled to another country
Contact your provider right away if you are an adult and you:
- Have a fever of 105°F (40.5°C) or higher, unless it comes down readily with treatment and you are comfortable
- Have a fever that stays at or keeps rising above 103°F (39.4°C)
- Have a fever for longer than 48 to 72 hours
- Have had fevers come and go for up to a week or more, even if they are not very high
- Have a serious medical illness, such as a heart problem, sickle cell anemia, diabetes, cystic fibrosis, COPD, or other long-term (chronic) lung problems
Heart problem
Heart disease often develops over time. You may have early signs or symptoms long before you have serious heart problems. Or, you may not realize y...
Read Article Now Book Mark ArticleSickle cell anemia
Sickle cell disease is a disorder passed down through families. The red blood cells that are normally shaped like a disk take on a sickle or crescen...
Read Article Now Book Mark ArticleDiabetes
Diabetes is a long-term (chronic) disease in which the body cannot regulate the amount of sugar in the blood.
Read Article Now Book Mark ArticleCystic fibrosis
Cystic fibrosis is a disease that causes thick, sticky mucus to build up in the lungs, digestive tract, and other areas of the body. It is one of th...
Read Article Now Book Mark ArticleCOPD
Chronic obstructive pulmonary disease (COPD) is a common lung disease. Having COPD makes it hard to breathe. There are two main forms of COPD:Chroni...
Read Article Now Book Mark Article - Have a new rash or bruises
- Have pain with urination
- Have a weakened immune system (from chronic steroid therapy, a bone marrow or organ transplant, spleen removal, HIV/AIDS, or cancer treatment)
HIV/AIDS
Human immunodeficiency virus (HIV) is the virus that causes acquired immunodeficiency syndrome (AIDS). When a person becomes infected with HIV, the ...
Read Article Now Book Mark Article - Have recently traveled to another country
Call 911 or the local emergency number if you or your child has a fever and:
- Is crying and cannot be calmed (children)
- Cannot be awakened easily or at all
- Seems confused
- Cannot walk
- Has difficulty breathing, even after the nose is cleared
- Has blue lips, tongue, or nails
- Has a very bad headache
- Has a stiff neck
- Refuses to move an arm or leg (children)
- Has a seizure
What to Expect at Your Office Visit
Your provider will perform a physical exam. This may include a detailed examination of the skin, eyes, ears, nose, throat, neck, chest, and abdomen to look for the cause of the fever.
Treatment depends on the duration and cause of the fever, as well as other symptoms.
The following tests may be performed:
- Blood tests, such as a CBC or white blood cell differential
CBC
A complete blood count (CBC) test measures the following:The number of white blood cells (WBC count)The number of red blood cells (RBC count)The numb...
Read Article Now Book Mark ArticleWhite blood cell differential
The blood differential test measures the percentage of each type of white blood cell (WBC) that you have in your blood. It also reveals if there are...
Read Article Now Book Mark Article - Urinalysis
Urinalysis
Urinalysis is the physical, chemical, and microscopic examination of urine. It involves a number of tests to detect and measure various compounds th...
Read Article Now Book Mark Article - X-ray of the chest
X-ray of the chest
A chest x-ray is an x-ray of the chest, lungs, heart, large arteries, ribs, and diaphragm.
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References
Leggett JE. Approach to fever or suspected infection in the normal host. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 264.
Nield LS, Kamat D. Fever. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 201.
Thermometer temperature - illustration
Fever is an important part of the body's defense against infection. Most bacteria and viruses that cause infections in humans thrive best at 98.6 degrees F (37 degrees C). Raising the body temperature a few degrees can help the body fight the infection. In addition, a fever activates the body's immune system to make more white blood cells, antibodies, and other infection-fighting agents.
Thermometer temperature
illustration
Temperature measurement - illustration
A thermometer is a useful aid used to measure body temperature.
Temperature measurement
illustration
Thermometer temperature - illustration
Fever is an important part of the body's defense against infection. Most bacteria and viruses that cause infections in humans thrive best at 98.6 degrees F (37 degrees C). Raising the body temperature a few degrees can help the body fight the infection. In addition, a fever activates the body's immune system to make more white blood cells, antibodies, and other infection-fighting agents.
Thermometer temperature
illustration
Temperature measurement - illustration
A thermometer is a useful aid used to measure body temperature.
Temperature measurement
illustration
Review Date: 7/3/2022
Reviewed By: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.