High body temperature, also known as a FEVER, is a common symptom of many illnesses. It is usually caused by the body's immune system responding to an infection or other foreign substance. A FEVER is typically defined as a body temperature that is higher than normal, which is usually around 98.6 degrees Fahrenheit. Fevers can range from mild to severe and can be accompanied by other symptoms such as chills, sweating, headaches, and fatigue. Treatment for a FEVER usually involves rest and hydration, as well as medications to reduce the body temperature.