heat exhaustion, condition caused by overexposure to sunlight or another heat source and resulting in dehydration and salt depletion, also known as heat prostration. The symptoms are severe headaches, weakness, dizziness, blurred vision, and sometimes unconsciousness. However, the body temperature is not elevated as in heatstroke heatstroke, profound disturbance of the heat-regulating mechanism of the body, also known as sunstroke. It is characterized by extremely high body temperatures and sometimes by convulsions and coma.
..... Click the link for more information. . The condition is usually temporary and rarely fatal. Water, mineral, and ion depletion may be so severe that painful spasms of the muscles, commonly called heat cramps, occur. Treatment includes administering a supplemental solution to replace the water, minerals, and ions that have been depleted from the body. See first aid first aid, immediate and temporary treatment of a victim of sudden illness or injury while awaiting the arrival of medical aid. Proper early measures may be instrumental in saving life and ensuring a better and more rapid recovery.
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heat exhaustion

or heat prostration

Response of the body to excessive heat. The body temperature rises moderately and heavy perspiration persists. Heat exhaustion results from inadequate water and salt intake and can lead to dehydration and collapse. It may progress to heatstroke if not treated by lying down in a cool place and drinking fluids, preferably water with salt added.

heat exhaustion [′hēt ig‚zȯs·chən]

(medicine)

A heat-exposure syndrome characterized by weakness, vertigo, headache, nausea, and peripheral vascular collapse, usually precipitated by physical exertion in a hot environment.