Fever is also known as hyperthermia, pyrexia, or elevated temperature. It describes a body temperature that’s higher than normal. Fever can affect children and adults. A short-term increase in body temperature can help your body fight off illness. However, a severe fever can be a symptom of a serious condition that requires immediate medical attention. Recognizing a fever can enable you to get treatment and proper monitoring for it.


Fever occurs when a part of the brain called the hypothalamus shifts the set point of your normal body temperature upward. When this happens, you may feel chilled and add layers of clothing or you may start shivering to generate more body heat. This eventually results in a higher body temperature.

There are numerous different conditions that can trigger fevers. Some possible causes include:

  • infections, including the flu, common cold, and pneumonia
  • some immunizations, such as diphtheria or tetanus (in children)
  • teething (in infants)
  • some inflammatory diseases, including rheumatoid arthritis and Crohn’s disease
  • sun stroke
  • food poisoning
  • some medications, including antibiotics

Depending on the cause of the fever, additional symptoms may include:

  • sweating
  • shivering
  • a headache
  • muscle aches
  • a loss of appetite
  • dehydration
  • general weakness

You or your child should also see a doctor as soon as possible if a fever is accompanied by any of the following symptoms:

  • a severe headache
  • throat swelling
  • a skin rash, especially if the rash gets worse
  • sensitivity to bright light
  • stiff neck and neck pain
  • persistent vomiting
  • listlessness or irritability
  • abdominal pain
  • pain when urinating
  • muscle weakness

Your doctor will probably perform a physical examination and medical tests. This will help him determine the cause of the fever and an effective course of treatment.