Heat exhaustion causes heavy sweating, weakness, and nausea, while heat stroke is an emergency with a body temperature over 103 F, confusion, and often no sweating. Call 911 for heat stroke.
Heat exhaustion
- Heavy sweating, weakness, headache, nausea.
- Cool, clammy skin.
- Body temperature under 104°F.
- Fix: move to shade, drink water, cool down.
Heat stroke
- Body temperature of 104°F or more.
- Hot, dry or damp skin, confusion, fainting.
- A medical emergency: call 911.
Treatment
Cool the person with ice or cold water while waiting for help.
Prevention
Hydrate and avoid peak heat.
Heat exhaustion symptoms
Heavy sweating, cool, moist or pale skin, fast weak pulse, muscle cramps, fatigue, dizziness, headache, nausea or vomiting, and fainting. The core temperature is generally below 104 degrees F (40 degrees C).
Heat stroke symptoms
Core temperature of 104 degrees F (40 degrees C) or higher, confusion, slurred speech, agitation, seizures, loss of consciousness, hot red skin that may be dry or damp and a fast strong pulse. Heat stroke is life threatening.
Key difference
The key difference is mental status and temperature. In heat stroke, the central nervous system fails, and body temperature control stops working. Untreated, it can cause organ damage or death within hours.
First aid for heat exhaustion
- Move to a cool, shaded or air conditioned place.
- Lie down with feet raised.
- Remove extra clothing.
- Sip cool water or a sports drink.
- Apply cool wet cloths or take a cool shower.
- Seek medical help if symptoms do not improve in 30 minutes, or if vomiting prevents drinking.
First aid for heat stroke
Call 911 immediately. Move the person to a cooler place and cool them quickly with cold water, ice packs on the neck, armpits and groin, or a cold water bath. Do not give fluids if unconscious.
Exertional heat stroke
Athletes and workers can develop heat stroke from intense activity even when fit. Cooling within 30 minutes of collapse greatly improves survival.
Who is at risk
Older adults, infants, people with chronic conditions, outdoor workers, athletes, and people taking certain medications.
Prevention
Drink fluids, rest in shade, wear light clothing, acclimatize over 1 to 2 weeks and never leave children or pets in cars.
Temperature thresholds and treatment
Heat exhaustion occurs when the body overheats, with heavy sweating, weakness, headache, nausea and a core temperature below about 104 F (40 C). Heat stroke occurs when the core temperature rises above 104 F with confusion, slurred speech, seizures or loss of consciousness, and it is a life threatening emergency. For heat exhaustion, move to a cool place, loosen clothing, sip water or sports drinks and apply cool cloths. For heat stroke, call 911 and cool the person immediately, ideally by immersion in cold water, which can lower temperature fastest.
Exertional cases and outcomes
Exertional heat stroke affects athletes, soldiers and outdoor workers, and cooling within 30 minutes greatly improves survival, using the principle “cool first, transport second” recommended by athletic training groups. Without prompt cooling, heat stroke can damage the brain, kidneys and muscles. The CDC reports thousands of heat related emergency department visits every summer. Acclimatize to heat over 1 to 2 weeks, hydrate, schedule breaks and avoid strenuous activity in the hottest part of the day. Do not give fluids to someone who is vomiting or unconscious.
Based on data from the CDC and the National Athletic Trainers’ Association
