The central nervous system maintains normal body temperature. When the body’s temperature rises, physiological systems transfer heat by sweating or increasing blood flow to the surface. Heat-related illnesses occur when the body loses the ability to transfer enough heat to cool the body sufficiently. There are a variety of illnesses directly related to heat that range in severity from mild to life-threatening.

Heat Rash

Often called prickly rash, the skin problem occurs when the ducts carrying sweat become plugged or swollen. The rash typically develops on areas of the body covered by clothing and appears as pink or reddish bumps that often itch. Untreated, the rash generally subsides naturally in a few days.

Heat Cramps

The malady involves brief muscle cramps or spasms that may include involuntarily jerking. Individuals often become afflicted with this form of muscle fatigue when exercising or working in excessive heat. The shoulders, thighs and calves are the areas most often affected. People are at the greatest risk of developing the condition after sweating extensively or drinking large quantities of plain water, which causes an electrolyte deficiency.

Heat Edema

Edema refers to a condition of fluid accumulation that produces swelling. When related to heat, the ailment most often occurs in the hands, legs and feet. Individuals experience the edema whether sitting or standing for long periods of time in extreme heat.

Heat Tetany

Tetany is a combination of hyperventilation and heat stress from being in a hot environment. The condition causes breathing difficulty, numbness or tingling and muscle spasms. Alleviating symptoms requires taking the affected individual out of the heat and coaching them to slow their respiration rate.

Heat Syncope

Syncope or fainting happens when the blood vessels dilate, blood flows downward into the legs and causes a sudden drop in blood pressure.

Heat Exhaustion

Also known as heat prostration, the condition develops after exercising or working in the heat and excessively sweating and not adequately replacing fluid and electrolytes. When caused by fluid depletion, symptoms include headache, thirst, generalized weakness and possible loss of consciousness. When the malady occurs because of an electrolyte imbalance, symptoms include dizziness, nausea and vomiting followed by muscle cramps. If not treated, heat exhaustion may progress to heat stroke.


Sometimes called sunstroke, the serious illness develops when the body cannot regulate body temperature, which may rise to 105 degrees F or higher. The condition is a medical emergency, may become life-threatening and can cause long-term effects. Symptoms often include:

* A throbbing headache
* Dizziness, light-headedness, fainting
* Lack of sweat
* Dry, hot, red skin
* Muscle cramps and weakness
* Nausea and vomiting
* A rapid heartbeat that may be strong or weak
* Rapid and shallow breathing
* Confusion, disorientation
* Lack of physical coordination
* Seizures