Heatstroke, heat exhaustion and dehydration: signs and first aid

Extreme heat kills more people than any other weather hazard in both Europe and the US. Most victims are older people, those with chronic illness or people who work outdoors. Almost all of these deaths are preventable if you recognize the signs in time and know what to do in the first minutes.

How to prepare for a heatwave is in our heatwave guide. This one is about first aid.

Recognize the signs

	Heat exhaustion	Heatstroke (emergency)
Skin	Cool, clammy, pale, heavy sweating	Hot, red, dry or damp
Temperature	Normal or slightly raised	Above 104 °F (40 °C)
Mental state	Conscious, tired, dizzy	Confused, agitated, slurred speech, seizures, fainting
Other	Nausea, headache, cramps, fast weak pulse	Fast strong pulse, rapid breathing
Action	First aid, then monitor	Call the emergency number and cool immediately

First aid for heat exhaustion

1. Move them to shade or a cool room.
2. Loosen tight clothing, remove extra layers.
3. Cool them: damp cloths, a water spray, a fan.
4. Give water or oral rehydration salts in small sips if they’re conscious.
5. Raise their legs if they feel faint.
6. If they don’t improve within 30–60 minutes, start vomiting or get worse, call the emergency number.

First aid for heatstroke

1. Call the emergency number.
2. Cool the person as fast as you can while you wait:
   • best, immersion in cold water up to the neck (bathtub, large tub), under supervision;
   • otherwise, soak the whole body with cold water and use a fan or create a draft;
   • ice packs or cold towels on the neck, armpits and groin.
3. Don’t give fluids if they’re confused or not swallowing well.
4. If they lose consciousness but are breathing, put them in the recovery position. If they’re not breathing, start CPR.

Dehydration

Signs in adults: thirst, dry mouth, little dark urine, fatigue, dizziness, headache.

Warning signs: confusion, no urine for 8 hours or more, very fast pulse, fainting. Call the emergency number or go to the ER.

What to do: drink water often, in small amounts. If you’ve sweated heavily or had diarrhea, use oral rehydration salts from a pharmacy. Keep a few sachets in your first aid kit.

Who’s most at risk

• Babies and young children: they can’t tell you they’re thirsty. Never leave them in a car, even for a minute.
• Older people: they feel thirst less and often take medicines that raise risk (diuretics, some blood pressure or psychiatric drugs). Call them daily during heatwaves.
• People with chronic illness: heart, kidney, diabetes.
• Outdoor workers and athletes.

Prevention

• Drink regularly, before you feel thirsty.
• Avoid the sun in the hottest hours, roughly 11 a.m. to 5 p.m.
• Loose, light-colored clothes and a hat.
• Keep your home cool: blinds closed by day, windows open at night.
• Lukewarm showers, cool compresses.
• Follow official heat warnings.