Susceptible to heat exhaustion

Heat exhaustion can develop when sweating and exertion cause the body to lose fluid and salt faster than they are replaced. Hot, humid conditions, direct sun, heavy clothing, intense activity, illness and some medicines can make temperature regulation harder. Early symptoms may include excessive sweating, thirst, headache, dizziness, weakness, nausea, cramps or dark urine. Heat intolerance can also make hot environments harder to tolerate, but a symptom alone does not confirm heat exhaustion.

Untreated heat exhaustion may progress to a dangerous heat illness. Dehydration can add to dizziness, reduced urination and fatigue, particularly when drinking has not kept pace with fluid loss.

Stop exercise or work and move to a cool, shaded or air-conditioned place. Loosen extra clothing, cool the skin with wet cloths or a fan, and sip water or an oral rehydration drink if the person is awake and able to swallow. Rest until symptoms have clearly settled, and avoid returning to strenuous activity in the same heat that day. A companion should stay nearby if dizziness or weakness is present.

For prevention, schedule demanding activity during cooler periods, take regular cooling breaks, wear loose breathable clothing and drink regularly rather than waiting for intense thirst. Ask a clinician about medicines or conditions that may affect sweating or fluid balance.

Get urgent medical help if there is confusion, fainting, a seizure, severe weakness, inability to drink, repeated vomiting, worsening headache, trouble breathing, or skin that is very hot with an altered mental state. Do not give fluids to someone who is unconscious or cannot swallow safely. Seek medical advice if symptoms do not improve promptly with cooling and fluids, or if dark urine and reduced urination continue.

Ask which medicines or health conditions could increase heat sensitivity, how much activity is reasonable in hot weather, and how to prepare for work, exercise or travel in a hot climate.