Key takeaways
- Heat exhaustion is a heat illness from overheating plus water and salt loss through heavy sweating.
- Symptoms: heavy sweating, weakness, dizziness, nausea, headache, and cool, clammy, pale skin.
- Treat it by stopping, cooling down, resting, and rehydrating (with water and electrolytes).
- If untreated, it can progress to life-threatening heat stroke — take it seriously.
This is general educational information, not medical advice. Heat illness can become life-threatening — when in doubt, cool the person and seek emergency medical help.
What heat exhaustion is
Heat exhaustion is a heat-related illness caused by the body overheating, typically with significant loss of water and salt through heavy sweating. It’s the body struggling to cope with heat — an important warning sign that sits between mild heat issues and the emergency of heat stroke.
Symptoms
Heavy sweating; weakness or fatigue; dizziness; nausea; headache; muscle cramps; and cool, clammy, pale skin (still sweaty, and usually still mentally clear). A fast, weak pulse and faintness can occur. Warning: if the skin becomes hot and dry and the person becomes confused, that signals heat stroke — a medical emergency.
On a hot, exposed climb, a hiker becomes weak, dizzy, and nauseated, drenched in sweat with clammy pale skin. Recognizing heat exhaustion, the group stops, gets them into shade, cools them with water and fanning, and has them sip an electrolyte drink — and they steadily recover.
Treatment and prevention
Treat: stop activity; get to cool shade; rest lying down; cool them (remove excess clothing, cool water, fan, cold packs to neck/armpits/groin); and rehydrate with water and electrolytes if alert. They should improve — if not, or if heat stroke signs appear, seek emergency help. Prevent: stay hydrated (avoid dehydration), replace electrolytes, pace yourself, rest in shade, avoid the hottest hours, and acclimatize to heat gradually. It’s part of the spectrum of hyperthermia.
The bottom line
Heat exhaustion is a heat illness from overheating and fluid/salt loss — heavy sweating, weakness, dizziness, nausea, and cool, clammy skin. It's a serious warning sign: stop, cool down, rest, and rehydrate, and the person should improve. If they don't, or if skin turns hot and dry and confusion sets in, that's heat stroke — a medical emergency. Prevent it with hydration, electrolytes, pacing, shade, and heat acclimatization.
Frequently asked questions
What is heat exhaustion?
Heat exhaustion is a heat-related illness that happens when your body overheats and loses too much water and salt, usually through heavy sweating in hot conditions or during strenuous activity. It's the body struggling to cope with heat, and it's an important warning sign that needs to be addressed promptly. It sits between mild heat issues and the medical emergency of heat stroke.
What are the symptoms of heat exhaustion?
Common symptoms include heavy sweating; weakness or fatigue; dizziness or lightheadedness; nausea (and sometimes vomiting); headache; muscle cramps; and cool, clammy, pale skin (the skin is typically still sweaty, unlike in heat stroke). A fast, weak pulse and feeling faint can also occur. Importantly, in heat exhaustion the person is still sweating and usually mentally clear; if the skin becomes hot and dry and the person becomes confused, that signals heat stroke — a medical emergency.
How do you treat and prevent heat exhaustion?
Treat it by stopping activity and getting the person to a cool, shaded place; having them rest and lie down; cooling them (remove excess clothing, apply cool water, fan them, cool packs to the neck/armpits/groin); and rehydrating with water and electrolytes if they're alert and able to drink. They should improve with cooling and rest — if they don't improve, worsen, or show signs of heat stroke, seek emergency help. Prevent it by staying hydrated, replacing electrolytes, pacing yourself, taking breaks in shade, avoiding the hottest hours, wearing appropriate clothing, and acclimatizing to heat gradually.
Sources
- Heat illness — Centers for Disease Control and Prevention
- Heat-related illness — American Red Cross