What causes heat stroke?

Heat stroke may follow prolonged time in hot or humid conditions, intense exercise, or work in protective clothing. It can also develop when heat exhaustion worsens and the body cannot replace fluid or shed heat quickly enough. Older adults, young children, people with chronic illness, and anyone taking medicines that affect sweating or fluid balance may be more vulnerable. Warning features include confusion, unusual behaviour, fainting, seizure, severe headache, vomiting, and very hot skin. Sweating may be present or absent, so it should not be used to rule heat stroke out.

Treat suspected heat stroke as an emergency. Call emergency services, move the person to shade or a cool place, remove excess clothing, and cool the skin rapidly with wet cloths, water, fans, or ice packs placed around the neck, armpits, and groin. Stay with them and monitor breathing. Do not give anything by mouth to a confused, unconscious, or vomiting person. Earlier [Heat Exhaustion](/conditions/heat-exhaustion/) can be a warning stage, but heat stroke requires emergency assessment.

Seek emergency care immediately for confusion, collapse, seizure, loss of consciousness, severe agitation, or very hot skin after heat exposure or exertion. Do not wait for the person to recover at home. Even if alertness improves during cooling, medical assessment is needed because heat stroke can affect the brain and other organs.

Ask what may have contributed, whether medicines or illness increased vulnerability, how to return safely to activity, and which cooling and hydration measures are appropriate for future hot weather.