What causes a fever?

Fevers are most often associated with bacterial or viral infections, such as:
  • cold
  • mumps
  • sore throat
  • measles
  • earache
  • pneumonia
  • diarrhea
  • bronchitis
  • urinary infection
  • appendicitis
  • roseola
  • meningitis
  • chickenpox
  • female reproductive infection
Diana Meeks
Diana Meeks on behalf of Sigma Nursing
Family Practitioner

A fever is a temporary increase in the body's temperature in response to some disease or illness. Some of the possible causes of a fever include:

  • Viruses
  • Bacterial infection
  • Heat exhaustion
  • Some malignant tumors
  • Blood clots or thrombophlebitis
  • Appendicitis
  • Tuberculosis
  • Skin infections or cellulitis
  • Some immunizations, such as the diphtheria, tetanus and acellular pertussis (DTaP) or pneumococcal vaccines
  • Exposure to extremely high temperatures
Sometimes the cause of a fever is not identifiable and the diagnosis may be fever of unknown origin.  

Although you feel lousy when you have a fever, a fever actually is good for you. Your increased body temperature stimulates white blood cells to produce antibodies, which fight off an infection. Some bacteria and viruses only can survive in a narrow temperature range, so heat can inhibit their production or kill them. A fever starts because the body's immune system identifies microbes from a bacteria or virus. The immune system then releases chemicals called cytokines into the bloodstream, which stimulate the body's thermostat, called the hypothalamus, in the brain. The hypothalamus raises the body's temperature by constricting blood vessels in the skin and causing skeletal muscles to contract, which makes us shiver.

Dr. Mehmet Oz, MD
Cardiologist (Heart Specialist)
A fever is your body’s normal response to infection in the form of an increased body temperature. Fevers can cause additional symptoms like shivering, sweating, or quickened breathing. Check for a fever by using a thermometer -- feeling someone’s forehead is not entirely accurate.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.