A fever is defined as any body temperature that is above the normal temperature of 98.6 F , or 37 C. The reading for adults is not considered significant until it goes over 100.4 F, or 38 C, according to MedicineNet.
When the body temperature rises because of a fever, it is a response mechanism of the immune system, states Scientific American. This kind of response is triggered when a foreign invader, such as bacteria, fungi, viruses, drugs or toxins, invades the system, notes MedicineNet. The body's temperature rises to fight off infections. Medicines that are used to reduce fever include acetaminophen, ibuprofen and aspirin. Aspirin should never to given to small children or infants.