Diarrhea and Heat Exhaustion

Heat exhaustion develops when the body struggles to cool itself and loses water or salts through sweating. Diarrhea adds another route of fluid loss. Together they may cause headache, dizziness, weakness, thirst, cramps, nausea, heavy sweating, or dark urine. Symptoms can progress quickly in hot or humid conditions, especially after exercise or time outdoors. The combination does not prove that heat is the only cause of diarrhea.

Stop activity, move to shade or an air-conditioned place, loosen extra clothing, and cool the skin with damp cloths or a fan. If the person is alert and able to swallow, give frequent small sips of water or an oral rehydration drink. Avoid alcohol. Rest and avoid returning to heat until fully recovered. Note sweating, urine colour, dizziness, and the timing of diarrhea so a clinician can judge fluid loss.

Call emergency services immediately for confusion, collapse, seizure, loss of consciousness, severe breathing difficulty, or very hot skin with a change in behaviour. Do not force drinks into someone who is drowsy or cannot swallow. Seek prompt care for persistent vomiting, worsening dizziness, very little or dark urine, severe weakness, or symptoms that do not improve after cooling and fluids. Heat illness may require medical assessment even without a measured fever.

How much fluid replacement is appropriate for me? Could an infection or medicine be contributing to the diarrhea? When is it safe to resume outdoor activity?