Fever
Fever occurs when your body temperature is elevated, often due to an illness. A fever is a response to inflammation and a reaction to foreign invaders in the body. A fever's purpose is to help the body fight off bacteria and viruses. Most fevers are treatable at home, but there are some that require medical attention.
While a body temperature of 99 to 100.3 degrees Fahrenheit is higher than normal, healthcare providers consider 100.4 F to be minimum that is called a fever.
This article covers the symptoms and types of fever, causes of fever, how to treat fever, and when to get help.
Symptoms of Fever
In addition to a temperature at or above 100.4 F, a fever can also include the following symptoms:
Chills and shivers
Excessive sweating
Fatigue
Joint, bone, or back pain
Muscle aches
Headache
Dehydration
In children, symptoms of fever can include:
Lower activity levels and staying quiet
Fussiness
Increased thirst and less hunger
Feeling warm
For about 3% of children aged 6 months to 5 years old, seizures called febrile convulsions can occur with a fever. Children who experience febrile convulsions usually outgrow them by 5 years of age.
Causes of Fever
Fever is usually a result of the immune system's fighting off an infection. The most common causes of fever are:
Respiratory viral or bacterial infections, including colds, flu, strep throat, sinus infections, ear infections, bronchitis, pneumonia, mononucleosis
Bacterial or viral gastroenteritis
Other bacterial infections, including skin infections
Other causes of fever include:
Vaccinations, which can cause one to two days of mild fever in children
Autoimmune disorders like rheumatoid arthritis or lupus
Early stage cancer
Blood clots
Environmental heal stress
What Medications Cause Fever?
"Drug fever" is the term for fever that is a side effect of a medication. Drug fever usually disappears soon after the medication is discontinued.
Medications that could cause fever include:
Anti-seizure medications
H2-blockers, which reduce acid in the stomach
Antibiotics
Antihistamines
How to Treat Fever
Mild fevers are usually treated at home with:
Rest
Getting more fluids, which can include drinking soup broth or sucking on ice pops
Removing extra clothing or heavy blankets, especially for young children and infants
A lukewarm bath after medication
Medications to treat fever include:
Over-the-counter (OTC) fever-reducing medications like Tylenol (acetaminophen) or Advil (ibuprofen) taken as advised
Aspirin (for adults only)
Healthcare provider-approved medications for babies under 3 months of age
The treatment of the underlying cause of the fever will vary. Bacterial infections may be treated with antibiotics. Viral infections will not respond to antibiotics and may only receive treatment to relieve the symptoms, or antiviral medication may be used.
Complications and Risk Factors Associated with Fever
Fevers require medical attention if they're 100.4 F or higher in children aged 0 to 24 months or 103 F or higher in older children and adults. If left untreated, complications of fever could include:
Febrile seizures with higher fevers in young children (in 2% to 5% of children under age 5)
Brain damage with fevers of 107 degrees or higher
Breathing issues
Death
Are There Tests to Diagnose the Cause of Fever?
A healthcare provider will measure a person's vital signs (body temperature, breathing rate, heart rate, and blood pressure) and take their report of symptoms, medical history, and list of medications. They will perform a physical examination which will look for signs of inflammation and infection.
To further determine the illness that may be causing a fever, they may perform these tests:
The following tests may be performed:
Rapid tests for influenza, strep throat, COVID-19, and respiratory syncytial virus (RSV)
Blood tests: A complete blood count may show an increased white blood cell count in the case of an infection.
Urinalysis: The presence of white blood cells, bacteria, and blood may indicate a urinary tract infection.
Chest X-ray: This may show pneumonia or other infections of the lungs and airways.
Bacterial cultures: A sample from the site of suspected infection (urine, sputum, swab, blood, spinal fluid) may be cultured in the lab to look for bacterial invaders, identify them, and determine their antibiotic susceptibility.
When to See a Healthcare Provider
Call your healthcare provider if a child:
Is 3 months or younger and has a rectal temperature of 100.4 degrees or higher
Is 3 month olds to 12 month olds and has a fever of 102.2 degrees or higher
Is younger than 2 and has a fever lasting longer than 24 to 48 hours
Is older and has a fever lasting 48 to 72 hours
Has a weakened immune system
Has other symptoms like a sore throat, cough, or earache
Has recently been to another country
Adults should see a healthcare provider if they:
Have a fever over 105 degrees
Have a fever that lasts longer than 48 to 72 hours
Have new rashes or bruises
Have pain when urinating
Have a heart problem, lung problem, or sickle cell anemia
Have recently been to another country
Seek emergency medical attention for anyone of any age who has a fever and:
Can't walk
Seems confused
Can't be awakened easily (if at all)
Has blue lips, nails, or tongue
Has a seizure
Has breathing difficulty
Abdominal pain
Summary
Fever is a temporary rise in body temperature as it fights off an infection. In addition to a higher temperature, symptoms of fever can include chills, sweating, fatigue, and body pains. Causes of fever include bacterial or viral infections such as the flu or cold, overdressing, autoimmune disorders, and vaccinations. Some medications can also cause fevers.
Treating fever usually includes getting rest and drinking fluids while stabilizing body temperature with lighter clothes and blankets. OTC pain medications like acetaminophen and ibuprofen can also be a part of the treatment.
Frequently Asked Questions
Why do fevers occur?
Fevers are usually a response to infections like bacteria or viruses. That's why they occur most often during illnesses like flu, cold, and pneumonia. Fevers can also be a part of autoimmune disorders like lupus or rheumatoid arthritis and conditions that weaken the immune system. At times, a high room temperature or intense emotions can also cause fever, as can medications, including antibiotics, antihistamines, and anti-seizure drugs.
When is a fever dangerous?
While most fevers can be treated at home, some fevers can be dangerous. For babies younger than 3 months, a fever 100.4 degrees requires medical attention, while children 3 months old to 12 months old usually require medical attention at a fever of 102.2 degrees or higher. For adults or older children, a fever of 103 degrees or higher might require urgent care. A fever of any temperature that persists for a week is likely something that requires help from a healthcare provider.
What are the most effective ways to treat fever?
Most fevers only require rest and fluids, however, over-the-counter medications can also help. Wearing lighter clothing and avoiding heavy blankets can also help with fever, as can a lukewarm bath after taking medication.