Since ancient times fever has been recognised as a sign of illness. In 400 B.C. the Greek physician Hippocrates prescribed the bark and leaves of the willow tree to relieve fever. These are now known to contain aspirin-like chemicals.
Some people still see it as a sign that the body is fighting illness.
The child becomes unusually sleepy or doesn't respond. The child won't take fluids. A child or adult has a stiff neck, an unusual rash or difficulty breathing. Fever, or pyrexia to give it its medical name, is caused by the release of certain chemicals by the immune system, usually as a result of infection or inflammation. In the past many infections were rapidly fatal and fever was greatly feared, whether due to measles, flu or after childbirth.