What should you know about exertional heat exhaustion?

Hard activity in a hot or humid environment produces heat faster than the body can release it. Sweating removes water and salts, so a person may develop weakness, headache, nausea, cramps, thirst, dizziness, or unusually heavy sweating. Read about [Heat Exhaustion](/conditions/heat-exhaustion/), [Excessive Sweating](/symptoms/excessive-sweating/), and [Heat Intolerance](/symptoms/heat-intolerance/).

Fluid loss can lead to [Dehydration](/conditions/dehydration/). Dark urine, thirst, and light-headedness may support that concern, but symptoms can overlap with other illnesses and should be judged in context.

Stop exercising and move to shade or an air-conditioned place. Lie or sit down, loosen unnecessary clothing, and cool the skin with wet cloths, fanning, or cool packs wrapped in fabric. If the person is awake and able to swallow, offer small, frequent sips of cool water or an oral rehydration drink.

Avoid alcohol and further exertion while recovering. Do not leave someone with worsening symptoms alone. A clinician should review ongoing vomiting, marked weakness, severe dizziness, or symptoms that do not improve after cooling and fluids.

Call emergency services for confusion, seizure, fainting, inability to drink, very hot skin, collapse, or a suspected progression to heatstroke. Emergency care is also needed when symptoms are severe, rapidly worsening, or fail to settle with first aid. Do not give fluids to someone who is unconscious or struggling to swallow.

Ask how much recovery time you need, when it is safe to return to exercise, whether medicines or medical conditions increase heat risk, and how to plan breaks, shade, clothing, and fluids for future activity.