Heat stress, heat exhaustion and heat stroke

Heat stress begins when the body struggles to lose heat and may cause thirst, tiredness, headache, dizziness, or heavy sweating. Heat exhaustion is more severe and can include weakness, nausea, clammy skin, rapid breathing, and reduced ability to continue activity. Heat stroke is life-threatening: the brain and other organs can be affected, with confusion, unusual behaviour, fainting, seizure, or collapse. Sweating may continue, so its presence does not rule out danger. [Heat Exhaustion](/conditions/heat-exhaustion/) and [Dehydration](/conditions/dehydration/) can overlap.

Stop activity and move the person to shade or air conditioning. Remove excess clothing, cool the skin with wet cloths or water, and fan continuously. If fully awake and able to swallow, offer small sips of water or a suitable rehydration drink. Never give fluids to someone who is confused, vomiting repeatedly, or unconscious. For suspected heat stroke, call emergency services immediately and continue cooling while waiting; do not leave the person alone.

Call emergency services for confusion, fainting, seizure, collapse, severe breathing difficulty, or a person who cannot drink safely. Urgent assessment is also needed when symptoms worsen, do not improve promptly with cooling, or include extreme weakness and persistent vomiting. Dark urine, severe dizziness, or intense thirst can signal substantial fluid loss and should not be ignored.

Ask how to plan fluids, clothing, shade, and rest during hot weather, and whether medicines or health conditions affect heat tolerance. Describe the setting, activity, symptoms, sweating, fluid intake, mental state, and how quickly cooling changed the condition.