Fever

  • Medical Author:
    John P. Cunha, DO, FACOEP

    John P. Cunha, DO, is a U.S. board-certified Emergency Medicine Physician. Dr. Cunha's educational background includes a BS in Biology from Rutgers, the State University of New Jersey, and a DO from the Kansas City University of Medicine and Biosciences in Kansas City, MO. He completed residency training in Emergency Medicine at Newark Beth Israel Medical Center in Newark, New Jersey.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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What causes a fever?

Fever is the result of an immune response by your body to a foreign invader. These foreign invaders include viruses, bacteria, fungi, drugs, or other toxins.

These foreign invaders are considered fever-producing substances (called pyrogens), which trigger the body's immune response. Pyrogens signal the hypothalamus in the brain to increase the body temperature set point in order to help the body fight off the infection.

Fever is a common symptom of most infections and thus a risk factor for fever is exposure to infectious agents. In children, immunizations (such as vaccine shots) or teething in may cause short-term low-grade fever. Autoimmune disorders, medication reactions, seizures, or cancers may also cause fevers.

Fever itself is not contagious; however, if the fever is caused by a viral or bacterial infection, the infection may be contagious.

What are the signs and symptoms of a fever?

A fever can cause a person to feel very uncomfortable. Signs and symptoms of a fever include the following:

  • Temperature greater than 100.4 F (38 C) in adults and children
  • Shivering, shaking, and chills
  • Aching muscles and joints or other body aches
  • Headache
  • Intermittent sweats or excessive sweating
  • Rapid heart rate and/or palpitations
  • Skin flushing or hot skin
  • Feeling faint, dizzy, or lightheaded
  • Eye pain or sore eyes
  • Weakness
  • With very high temperature (> 104 F/40 C), convulsions, hallucinations, or confusion is possible...Seek medical attention.

How is a fever diagnosed?

Along with having generalized symptoms of a fever, taking one's temperature with a thermometer can confirm the diagnosis of a fever. A temperature greater than 100.4 F in adults or children is considered a fever.

Different tests may be done by a doctor, such a blood and imaging tests, to determine the cause of a fever and if the cause of the fever needs to be treated.

Medically Reviewed by a Doctor on 2/4/2016

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