Heat Exhaustion vs. Heat Stroke: Symptoms, Differences, And First Aid

Header image: U.S. Department of Energy

Quick Answer

Heat exhaustion is the body's response to losing too much water and salt through sweating. Symptoms include heavy sweating, headache, nausea, dizziness, weakness, and thirst. Heat stroke is a medical emergency in which the body can no longer control its temperature. The biggest warning sign is a change in mental state: confusion, slurred speech, seizures, or passing out. For heat stroke, call 911 and cool the worker immediately. Body temperature can reach 106°F within 10 to 15 minutes.

Heat Exhaustion vs. Heat Stroke At A Glance

	Heat exhaustion	Heat stroke
What it is	The body losing too much water and salt, usually through heavy sweating	The body can no longer control its temperature. Sweating may fail and core temperature rises fast
Severity	Serious. Can progress to heat stroke	Life-threatening medical emergency
Skin and sweat	Heavy sweating	Hot, dry skin or profuse sweating
Mental state	Irritable, but alert	Confusion, slurred speech, loss of consciousness
Other signs	Headache, nausea, dizziness, weakness, thirst, decreased urine output	Seizures, very high body temperature
Body temperature	Elevated	Very high. Can reach 106°F or more within 10 to 15 minutes
First move	Remove from heat, give fluids, get medical evaluation	Call 911 and start cooling immediately

Source: NIOSH, Heat-related Illnesses.

The One Sign That Matters Most: Confusion

Sweating is not a reliable way to tell the two apart. NIOSH lists both hot, dry skin and profuse sweating as possible heat stroke symptoms, so a worker can still be sweating heavily and be having a heat stroke. The clearest dividing line is the brain. A worker with heat exhaustion feels terrible but can still answer questions. A worker who is confused, slurring, acting strangely, having a seizure, or losing consciousness should be treated as having heat stroke until a medical professional says otherwise.

Heat Exhaustion: Symptoms And First Aid

NIOSH lists these heat exhaustion symptoms: headache, nausea, dizziness, weakness, irritability, thirst, heavy sweating, elevated body temperature, and decreased urine output.

First aid for heat exhaustion:

1. Take the worker to a clinic or emergency room for evaluation. Call 911 if medical care is not available.
2. Have someone stay with the worker.
3. Move the worker out of the heat and give liquids to drink.
4. Remove unnecessary clothing, including shoes and socks.
5. Cool the worker with cold compresses or have them wash their head, face, and neck with cold water.
6. Encourage frequent sips of cool water.

Do not send a worker with heat exhaustion back into the heat the same day. Heat exhaustion can progress to heat stroke, and symptoms that get worse are a reason to call 911.

Heat Stroke: Symptoms And First Aid

NIOSH lists these heat stroke symptoms: confusion, altered mental status, or slurred speech; loss of consciousness; hot, dry skin or profuse sweating; seizures; and very high body temperature. Heat stroke can be fatal if treatment is delayed.

First aid for heat stroke:

1. Call 911.
2. Stay with the worker until emergency medical services arrive.
3. Move the worker to a shaded, cool area and remove outer clothing.
4. Cool the worker quickly: a cold water or ice bath if possible, or wet the skin, place cold wet cloths on the skin, and soak clothing with cool water.
5. Circulate air around the worker to speed cooling.
6. Place cold wet cloths or ice on the head, neck, armpits, and groin.

Cooling comes first. Every minute at a dangerously high core temperature increases the risk of permanent damage or death, so start cooling while you wait for EMS.

Other Heat Illnesses To Know

• Heat cramps: painful muscle cramps or spasms from losing salt and moisture. They can also be a symptom of heat exhaustion.
• Heat syncope: fainting or dizziness after standing too long or standing up suddenly, often linked to dehydration and lack of acclimatization.
• Rhabdomyolysis: rapid muscle breakdown from heat and heavy exertion. Watch for muscle pain, weakness, and dark, tea- or cola-colored urine. Workers need immediate medical care.
• Heat rash: red clusters of small pimples or blisters caused by heavy sweating.

Preventing Both

Heat exhaustion and heat stroke are preventable. The basics are water, rest, shade, acclimatization for new and returning workers, and a crew trained to spot symptoms early. For the full prevention program, see preventing heat stress on the jobsite.

Heat Illness Key Facts

Confusion = emergency: any change in mental state in the heat means treating it as heat stroke and calling 911.

106°F in 10 to 15 minutes: how fast body temperature can rise in heat stroke (NIOSH).

Sweating does not rule out heat stroke: skin can be hot and dry or sweating heavily.

Cool first: start rapid cooling while waiting for EMS.

Cooling Gear From BDG Safety

Evaporative cooling. PIP EZ-Cool evaporative cooling towel | PIP evaporative cooling neck wrap | PIP evaporative cooling vest | PIP cooling hard hat pad with neck shade

Sun and neck shades. Studson SHK-1 neck shade | Pyramex SL T2 neck shade | PIP sun shade extensions for full brim hard hats | PIP hi-vis evaporative cooling neck shade

Breathable hi-vis and sweat control. Kishigo all mesh contrast vest | Kishigo Cool Touch Class 3 short sleeve shirt | Hardknock sweatband for Resolve helmets | PIP cellulose sponge sweatband

Related Weather And Seasonal Safety Resources

Preventing heat stress on the jobsite. Water, rest, shade, and a written plan.

Cold weather work gloves. Protecting hands in winter.

What is PPE? Choosing gear that protects and gets worn.

Choosing the right safety helmet. Vented options for hot work.

Frequently Asked Questions About Heat Exhaustion And Heat Stroke

Q: What is the main difference between heat exhaustion and heat stroke?

A: Heat exhaustion is the body struggling with water and salt loss. The worker is uncomfortable but alert. Heat stroke is the body's temperature control failing, and it causes confusion, seizures, or loss of consciousness. Heat stroke is a 911 emergency.

Q: Can you still sweat with heat stroke?

A: Yes. NIOSH lists hot, dry skin or profuse sweating as heat stroke symptoms, so sweating does not rule it out.

Q: Can heat exhaustion turn into heat stroke?

A: Yes. That is why a worker with heat exhaustion should get medical evaluation, be cooled, and not return to hot work that day.

Q: Should you give water to someone with heat stroke?

A: Focus on calling 911 and cooling the worker. Do not force fluids on someone who is confused or unconscious.

Prepare Your Crew For The Heat

BDG Safety helps contractors, facility managers, and contracting officers outfit crews for hot weather with cooling towels, neck shades, cooling vests, and breathable hi-vis. Call (619) 992-7621 or email info@bulldoggroup.net. BDG Safety is a Navy-veteran-founded, certified Service-Disabled Veteran-Owned Small Business (SDVOSB) that supplies Type II safety helmets and PPE to contractors, agencies, and the U.S. Army Corps of Engineers. Real people who know the gear, no phone menus. Open a B2B account or see how to buy.

Explore more guides in the BDG Safety Resource Center.