Heat Exhaustion vs. Heat Stroke: Know the Difference — It Could Save a Life

Both are heat-related illnesses, but heat stroke is a medical emergency; heat exhaustion is a warning. Recognizing the difference determines urgency.

Heat Exhaustion (Heat Stress)

Pathophysiology

Volume depletion + electrolyte loss from sweating → inadequate cardiac output for thermoregulation + perfusion.

Symptoms

• Heavy sweating (skin cool, clammy)
• Weakness, fatigue, dizziness
• Nausea, vomiting
• Headache
• Muscle cramps
• Normal or mildly elevated temperature (<104°F / 40°C)
• Mental status: Alert, may be anxious

Treatment

• Move to cool/shaded area.
• Remove excess clothing.
• Cool with wet cloths, fan, cool shower.
• Oral rehydration: water + electrolytes (ORS, sports drink).
• Monitor — if no improvement in 30 min or worsens → EMS.

Heat Stroke (Medical Emergency)

Pathophysiology

Thermoregulatory failure → core temperature >104°F (40°C) → direct thermal injury to cells, proteins, membranes → multi-organ dysfunction.

Symptoms

• Core temp >104°F (40°C) (rectal most accurate)
• Hot, dry skin (sweating may be absent — but not always)
• Rapid, strong pulse; rapid breathing
• Altered mental status: Confusion, agitation, seizures, coma
• Nausea, vomiting, headache

Immediate Action

1. Call 911.
2. Aggressive cooling while waiting:
   • Cold water immersion (best) — ice water bath.
   • Ice packs to neck, axillae, groin.
   • Evaporative: spray cool water + fan.
3. Do NOT give fluids if altered mental status (aspiration risk).
4. Monitor ABCs; CPR if needed.

Comparison

Cool, clammy, sweaty

Feature	Heat Exhaustion	Heat Stroke
Core temp	<104°F	>104°F
Skin	Hot, usually dry
Mental status	Normal	Altered (confusion, seizure, coma)
Urgency	Urgent	EMERGENCY

Prevention

• Hydrate proactively (pale urine).
• Acclimatize to heat over 7–14 days.
• Light, loose, light-colored clothing.
• Schedule exertion for cooler hours.
• Check on vulnerable: elderly, children, chronic illness, no AC.

Heat exhaustion → treat on site. Heat stroke → cool first, transport second. Every minute of delay increases mortality.