First aid for heat exhaustion

Heat exhaustion develops when sweating and fluid loss make it harder for the body to control its temperature. The person may feel weak, dizzy or headachy, with clammy skin, thirst and heavy sweating. Dark urine can point to dehydration. Heat exhaustion can worsen quickly, especially after exertion, in humid weather or when fluid intake has been low.

The condition is different from heatstroke, in which altered behaviour, confusion, seizures or collapse are emergency signs. A person with heat exhaustion should not be left alone while they cool down.

Stop activity and help the person rest in shade or an air-conditioned room. Remove unnecessary outer layers and cool the skin with wet cloths, a fan or a cool shower. Offer water or an oral rehydration drink in small, repeated sips if they are awake and able to swallow. Do not force drinks if they are vomiting, drowsy or confused. Avoid alcohol and strenuous activity until fully recovered.

Call emergency services if the person is confused, has a seizure, faints, cannot drink, has trouble breathing, or remains very hot despite cooling. Seek medical assessment if symptoms do not improve promptly, vomiting prevents hydration, or the person is pregnant, elderly, very young, or has a serious medical condition. Recurrent symptoms during heat exposure also deserve review.

Ask whether medicines or a health condition increase your heat risk, how much fluid is suitable for you, and how to plan exercise or outdoor work in hot weather.