If someone is having a heat stroke, call emergency services immediately and start cooling them down as fast as possible. Heat stroke is a life-threatening emergency where the body’s core temperature rises dangerously high and the brain starts to malfunction. Every minute of delay increases the risk of organ damage or death. While you wait for paramedics, your single most important job is to lower that person’s body temperature by any means available.
How to Recognize Heat Stroke
Heat stroke looks different from ordinary overheating. The hallmark sign is a change in mental status: confusion, slurred speech, agitation, irritability, or complete loss of consciousness. A person who was just tired and sweaty a few minutes ago may suddenly seem disoriented, unable to answer simple questions, or may collapse. Seizures can also occur.
The person’s skin may be hot and dry, or they may still be sweating heavily, especially if the heat stroke developed during exercise. Either presentation counts. If someone has been in the heat and is now confused, acting strangely, or unresponsive, treat it as heat stroke and act immediately.
Step 1: Call 911
Heat stroke requires hospital care. Do not wait to see if the person improves on their own. Call emergency services first, then begin cooling. If you’re with other people, have one person make the call while you start the steps below.
Step 2: Cool Them Down Aggressively
Cold water immersion is the single most effective cooling method. If you have access to a tub, kiddie pool, or even a large trough, fill it with cold water and ice and get the person into it. This approach lowers core body temperature at roughly 0.13°C per minute, which is more than twice as fast as any other technique. Massage their arms and legs while they’re in the water to keep blood circulating to the skin’s surface, where it can release heat.
If immersion isn’t possible, the next best option is evaporative cooling. Spray or sponge the person’s skin continuously with water while fanning them. This mimics how sweat works and cools at about 0.05°C per minute. Use whatever you have: a garden hose, spray bottles, wet towels, or soaked clothing combined with a fan or vigorous hand-fanning.
Placing ice packs on the neck, armpits, and groin can help as a supplement but is less effective on its own. These areas have large blood vessels close to the skin, so the cold transfers into the bloodstream, but the cooling rate is slower than immersion or evaporation. Use ice packs as an add-on, not a replacement, for the methods above.
Step 3: Move Them to a Cool Environment
Get the person out of direct sunlight and into the coolest area available. An air-conditioned room is ideal. If you’re outdoors, move them into shade. Remove any unnecessary clothing to expose as much skin as possible to the air and to your cooling efforts. Loosen anything tight around the neck or chest.
What Not to Do
Several common instincts can actually make things worse during heat stroke:
- Don’t give aspirin or acetaminophen. Heat stroke isn’t a fever. These medications won’t lower the temperature and can worsen liver injury and blood clotting problems that heat stroke already causes.
- Don’t give anything by mouth if the person is confused, vomiting, or unconscious. They could choke. Fluids need to go through an IV at the hospital in these cases.
- Don’t give alcohol or caffeine. Both interfere with the body’s ability to regulate temperature.
- Don’t use rubbing alcohol on the skin. It can be absorbed and cause additional harm.
- Don’t give salt tablets. Electrolyte correction needs to happen carefully in a medical setting, because overcorrecting sodium levels can cause brain swelling and permanent damage.
What Happens at the Hospital
Paramedics and emergency physicians will continue aggressive cooling and begin replacing fluids through an IV. The priority is restoring normal body temperature as quickly as possible while supporting blood pressure and circulation. Rapid cooling typically improves mental status fast, so even a person who seemed deeply unconscious may begin to wake up once their temperature drops.
Doctors will monitor for damage to the kidneys, liver, heart, and brain, all of which are vulnerable during heat stroke. Blood tests and heart monitoring are standard. Most people with mild to moderate liver injury from heat stroke recover fully, with liver function returning to normal within about 2 to 16 days.
Potential Long-Term Effects
The brain is especially vulnerable to heat damage, and the cerebellum (the region that controls coordination and balance) is the most susceptible area. Some people recover completely with no lasting effects, particularly when cooling began quickly. Others may experience lingering problems with coordination, memory, or concentration. In some cases, cerebellar damage doesn’t show up on brain scans until months or even years later, which is why follow-up care matters even after someone seems to have recovered.
The heart can also sustain damage during heat stroke, though it often recovers without lasting structural changes. High body temperatures trigger intense inflammation throughout the body, similar to what happens during sepsis, and this systemic stress is what drives damage across multiple organs simultaneously.
Heat Exhaustion vs. Heat Stroke
Heat exhaustion is the stage before heat stroke and is much less dangerous. A person with heat exhaustion feels weak, nauseous, dizzy, and sweats heavily, but their mental function stays intact. They can still think clearly, answer questions, and follow instructions. Once confusion, bizarre behavior, slurred speech, or loss of consciousness appears, the situation has crossed into heat stroke territory and becomes a medical emergency.
If you catch someone in the heat exhaustion phase, move them to a cool place, give them water in small sips, and apply cool compresses. This can prevent progression to heat stroke. But if their mental state changes at any point, stop treating it as something you can manage on your own and call for emergency help.