Normally, humans adjust to excessive temperatures by complex cardiovascular and neurologic changes that are coordinated by the hypothalamus. Heat loss offsets heat production to regulate the body temperature. This is done by evaporation (sweating) or vasodilation, which cools the body’s surface by radiation, conduction, and convection.

Heat production increases with exercise, infection, and use of drugs such as amphetamines.

Heat loss decreases with high temperatures or humidity, lack of acclimatization, excess clothing, obesity, dehydration, cardiovascular disease, sweat gland dysfunction, and use of drugs, such as phenothiazines and anticholinergics.

When heat loss mechanisms fail to offset heat production, the body retains heat and heat syndrome may develop.