A fever is a body temperature that is higher than normal. It is not an illness. It is part of your body's defense against infection. Most bacteria and viruses that cause infections do well at the body's normal temperature (98.6 F). A slight fever can make it harder for them to survive. Fever also activates your body's immune system.

Infections cause most fevers. There can be many other causes, including

• Medicines
• Heat exhaustion
• Cancers
• Autoimmune diseases

Treatment depends on the cause of your fever. Your health care provider may recommend using over-the-counter medicines such as acetaminophen or ibuprofen to lower a very high fever. Adults can also take aspirin, but children with fevers should not take aspirin. It is also important to drink enough liquids to prevent dehydration.