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. 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.