Why does heat exhaustion cause excessive sweating?

When the body becomes too warm, the nervous system signals sweat glands to produce fluid on the skin. As sweat evaporates, it carries heat away. During Heat Exhaustion, hot weather, strenuous activity, humidity, or heavy clothing can make cooling difficult, so sweating may become heavy and the body loses water and salts.

Other symptoms can include thirst, weakness, headache, dizziness, nausea, muscle cramps, cool clammy skin, and a fast pulse. Heavy sweating can also occur for other reasons, so the surrounding heat and the wider symptom pattern matter. Heat illness can worsen quickly if cooling and hydration do not help.

Stop exertion and move to a shaded or air-conditioned place. Remove excess clothing, loosen tight layers, and cool the skin with wet cloths or a fan. Sip cool water or an oral rehydration drink if the person is awake and able to swallow. Rest and avoid returning to heat or exercise until fully recovered. Do not force fluids in someone who is confused or vomiting.

Call emergency services for confusion, fainting, seizures, severe weakness, inability to drink, or very hot skin, because these may signal heatstroke. Seek medical care if symptoms do not improve promptly with cooling and fluids, or if the person is pregnant, very young, older, or has a condition that affects fluid balance.

Ask how to replace fluids safely, whether medicines or a health condition increase heat risk, and when it is safe to resume outdoor activity or exercise.