Symptoms of hyperthermia, or heat-related illness, vary according to the specific type of illness. The most severe form of hyperthermia is heat stroke. This happens when the body is no longer able to regulate its internal temperature; this is a medical emergency. The body temperature may be over 105 F, a level that damages the brain and other organs. Other symptoms include muscle cramps, fatigue, dizziness, headache, nausea, vomiting, and weakness. The heart rate may be elevated, and the skin is reddened. The skin may be moist if sweating is still occurring, or it may be dry if sweating has stopped. Confusion and mental changes may develop, and seizures can occur with brain damage. Ultimately, coma and death may ensue.
Heat exhaustion is a less severe form of hyperthermia. People with heat exhaustion typically experience weakness, nausea, vomiting, headache, muscle cramps, and profuse sweating. Other forms of heat illness include heat cramps, which are involuntary spasms of large muscle groups, and heat syncope, which is fainting or lightheadedness. Heat rash is characterized by a prickly or itchy feeling of the skin coupled with red bumps on the skin.