Why does heat stroke cause fainting?

With severe heat illness, the body may be unable to control its temperature. Blood pressure and circulation can become unstable, while the brain becomes affected by the heat itself. A person may feel unsteady before collapsing, or may become confused, agitated, drowsy or unresponsive. Fainting is a common presentation of Heat Stroke. Fainting has other possible causes too, but collapse during or after heat exposure is an emergency warning sign.

Call emergency services now. Move the person to a shaded or air-conditioned place, remove excess clothing and begin active cooling with cool water, wet cloths, a fan or ice packs wrapped in cloth at the neck, armpits and groin. Keep them lying down and monitor breathing. If they are unconscious, having a seizure, confused or unable to swallow, do not give anything to drink.

Any fainting, new confusion, seizure, collapse or loss of alertness in hot conditions requires emergency care. Continue cooling while help is on the way. If the person is not breathing normally, follow emergency call-handler instructions and start resuscitation if you are trained. Do not wait to see whether they recover fully before seeking help.

After emergency assessment, ask when it is safe to return to work, sport or outdoor duties. Discuss prior fainting, medicines, hydration habits and any heart or neurological conditions that may need further evaluation.