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What is fever?

Fever is an increase in your body’s temperature to a range that is above normal (98.6°F). Normal body temperature can change throughout the day by a few degrees. Various factors can increase your body temperature. Examples include infection, eating, physical activity, medications, surrounding (room or outdoor) temperature, or a strong emotional response.

An oral temperature of 99.5°F in a child and over 99 to 99.5°F in adults is considered a fever. Fever causes include benign conditions, such as a cold, and serious conditions, such as influenza and meningitis. Infant teething, recent immunization, autoimmune and inflammatory disorders, and some cancers can cause a fever as well.

An extremely high fever temperature can lead to seizures (called a febrile seizure) in children. These seizures do not usually cause permanent harm, but you should visit your healthcare provider if your child experiences a seizure. Seek emergency care if a seizure lasts more than a couple of minutes.

If your fever lasts more than 48 hours, occurs with other alarming signs, or causes you concern, seek prompt medical care. Fever in infants and very young children can quickly become serious, so exercise caution if your baby develops a fever. Seek immediate medical care (call 911) if you, or someone you are with, have a fever with difficulty breathing, stiff neck, or confusion. These are potential signs of a serious or life-threatening illness that needs immediate evaluation in an emergency setting.

What other symptoms might occur with fever?

Other symptoms may accompany a fever, depending on the underlying disease, disorder or condition. Fever is usually a sign of infection, which often leads to a variety of symptoms. This section describes relatively common as well as more serious symptoms that may occur along with a fever.

Symptoms may occur along with fever

Fever may occur with other common symptoms including:

  • Cough and upper respiratory congestion
  • Decreased urine output
  • Earache
  • Flushed face
  • General ill feeling
  • Hot, dry skin
  • Lethargy
  • Nausea
  • Rash
  • Thirst
  • Vomiting

Serious fever symptoms that might indicate a life-threatening condition

In some cases, fever may occur with other symptoms and certain combinations of symptoms that might indicate a serious or life-threatening condition that should be immediately evaluated in an emergency setting. Be particularly concerned about fever in infants two months of age or younger.

Seek immediate medical care (call 911) if you, or someone you are with, have any of these life-threatening symptoms:

  • Bluish coloration of the lips or fingernails
  • Change in level of consciousness or alertness, such as passing out or unresponsiveness
  • Change in mental status or sudden behavior change, such as confusion, delirium, lethargy, hallucinations and delusions
  • Crying inconsolably
  • Extremely watery diarrhea, possibly with blood
  • High fever (higher than 101°F)
  • Respiratory or breathing problems, such as shortness of breath, difficulty breathing, labored breathing, wheezing, not breathing, and choking
  • Seizure
  • Very bad headache

What causes fever?

The presence of natural proteins called cytokines help manage body temperature. A flood of specific cytokines (pyrogens) within the circulation will generate fever. Multiple types of infections, inflammatory disorders, and conditions can lead to a fever.

More common infections include flu (influenza), pneumonia, appendicitis, and urinary tract infections. Rheumatoid arthritis and other connective tissue inflammatory conditions can also be present with a fever. Your baby may even have a fever when teething. Because there are so many possibilities, it is important to contact your doctor to address your concerns and answer your questions.

Possible causes of fever

Fever is a sign of many different types of infections:

  • Abscess
  • Appendicitis
  • Gallbladder disease
  • Urinary tract infection

Other causes of fever

Fever can also be caused by inflammatory conditions including:

  • Arthritis
  • Autoimmune disorders
  • Rheumatoid arthritis (chronic autoimmune disease characterized by joint inflammation)
  • Systemic lupus erythematosus (disorder in which the body attacks its own healthy cells and tissues)

Life-threatening causes of fever

In some cases, fever may be a symptom of a serious or life-threatening condition that should be immediately evaluated in an emergency setting. These conditions include:

  • Epiglottitis (life-threatening inflammation and swelling of the epiglottis, a tissue flap between the tongue and windpipe)
  • Influenza, particularly in the very old or young
  • Meningitis (infection or inflammation of the sac around the brain and spinal cord)
  • Pericarditis
  • Septic shock
  • Tuberculosis (serious infection affecting the lungs and other organs)

When should you see a doctor for fever?

A fever is not necessarily always a reason to call your doctor or see one. Most causes of fever are not serious and the problem resolves on its own. But there are circumstances that warrant medical advice and attention.

Fever in children

Fevers can be a concern for babies because it can lead to problems quickly. With older children, there usually is not cause for alarm as long as they are responsive and drinking fluids.

Call your child’s doctor right away when:

  • A rectal temperature of 100.4°F or higher occurs in a baby younger than three months.
  • Fever goes above 104°F or higher in a child of any age.
  • Fever persists for more than 24 hours in a child younger than two years or for more than 72 hours in a child two years old or older.
  • Other symptoms occur including ear pain, cough, sore throat, or pain with urination.
  • Your child is taking medicines that suppress the immune system, has recently received a vaccine, or has immune system problems or serious medical conditions.
  • Your child seems to be getting worse or still seems sick despite bringing down the fever.

Call 911 or go to your nearest emergency room for fever when:

  • Other symptoms occur including recurrent vomiting or diarrhea, unexplained rash or bruising, stiff neck, or severe headache.
  • Seizures occur with a fever.
  • Your child has been in a very hot place, such as an overheated car.
  • Your child has signs of dehydration, including dry mouth and tongue, no tears with crying, no wet diapers for three hours, and sunken eyes, cheeks, or soft spots.
  • Your child is very fussy, irritable, listless, drowsy or lethargic.

Fever in adults

Adults should contact their doctor for a fever when:

  • Fever is 103°F or higher.
  • Fever lasts for more than 48 hours.
  • Low fevers come and go for a week or more.
  • Other symptoms occur including cough, sore throat, or pain with urination.
  • You take medicines that suppress the immune system, have recently traveled outside the country, or have immune system problems or chronic medical conditions, such as diabetes or heart problems.

Call 911 or go to your nearest emergency room for fever when:

  • Other symptoms occur including confusion, unexplained rash or bruising, stiff neck, sensitivity to light, or severe headache.
  • Seizures occur with a fever.
  • You have symptoms of dehydration, including excessive thirst, dark-colored urine, urinating less than normal, headache, skin that remains raised after pinching it, or dizziness, lightheadedness or fainting.

How do doctors diagnose the cause of fever?

The initial evaluation of a fever will start with a physical exam and medical history. The exam will focus on potential sources of the fever or an infection. Your doctor will likely pay special attention to the ears, nose, throat, skin and abdomen. Your doctor will also listen to your heart and lungs.

Questions for diagnosing the cause of fever

To diagnose the underlying cause of fever, your doctor may ask you several questions related to your symptoms. Questions for diagnosing the cause of fever include:

  • When did the fever start?
  • How long have you had a fever?
  • Is the fever constant or intermittent?
  • Is the fever reduced by common over-the-counter medications, such as acetaminophen (Tylenol)?
  • Do you have any other symptoms, such as a cough or sore throat?
  • Have you recently traveled outside the country or been around anyone who is sick?
  • Have you recently had surgery or an immunization?
  • What other medical conditions do you have?
  • What medications do you take?

Depending on your answers and the results of the physical exam, your doctor may order testing. This could include nose or throat swabs, blood tests, urinalysis, or chest X-ray.

What are the treatments for fever?

Fever treatment depends on the cause of the fever and your comfort. Low-grade fevers can actually be helpful for fighting some infections. However, high fevers can make you uncomfortable and make it hard for you to care for yourself.

To bring a fever down, medication options include acetaminophen (Tylenol) and ibuprofen (Advil, Motrin). Follow dosing instructions on the bottle or contact your doctor or pharmacist for advice. Avoid giving aspirin to children with a fever due to the risk of Reye’s syndrome, which can be fatal.

If an infection is causing your fever, additional medicines may be necessary. Antibiotics can treat bacterial infections, such as strep throat or a urinary tract infection. However, antibiotics will not work for viral infections. There are a few antiviral medicines that can treat certain diseases, such as influenza. But the best treatment for viral infections is usually rest and fluids to prevent dehydration.

In newborn infants, fever can be especially dangerous. In some cases, doctors may recommend hospitalization for safety.

Home remedies for fever

There are several home remedies for fever to help bring it down and keep you comfortable. This includes:

  • Dressing in layers and using layers of sheets and covers so you can adjust your comfort with chills and sweats. Avoid overly bundling in clothes and blankets.
  • Drinking plenty of fluids to prevent dehydration. Water, broths, and rehydration solutions are the best choices.
  • Eating what appeals to you to keep your strength
  • Resting to allow your body to recover and avoiding physical activity, which can increase your body temperature. It is generally okay to let your child play quietly if he or she feels like it.
  • Taking a lukewarm bath. Avoid cold baths or alcohol rubs, which are counterproductive. They cool the skin, but can cause shivering that increases body temperature.

What are the potential complications of fever?

A rise in temperature is your body’s natural way of killing the infectious agent or preventing its spread. A fever is a sign of an infectious or inflammatory process, many of which can be treated without serious difficulties. In most cases, the complications are due to the underlying problem, not the fever itself. However, there are potential complications of untreated or poorly controlled fever, some of which can be serious and even life-threatening including:

  • Dehydration due a decreased desire to drink fluids
  • Long term physical disability
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Apr 28
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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