Heat exhaustion occurs when a person can't sweat enough to cool
the body. It generally develops when a person is working or exercising in hot
weather.
Symptoms of heat exhaustion include fatigue, weakness, headache,
dizziness, or nausea, and the skin is pale, cool, and moist. Mild heat
exhaustion does not cause a change in a person's mental alertness and usually
can be treated at home.
Moderate to severe heat exhaustion can sometimes lead to
heatstroke, which requires emergency treatment.