Heat stroke is treated by cooling the body as fast as possible, ideally through cold water immersion from the neck down. The core principle is “cool first, transport second,” because every minute of dangerously high body temperature increases the risk of organ damage. Whether you’re helping someone on a soccer field or waiting for paramedics, rapid cooling is the single most important intervention.
Why Speed Matters
Heat stroke occurs when the body’s core temperature rises above 40°C (104°F) and the brain and organs start to malfunction. At that temperature, proteins in cells begin to break down, and prolonged exposure can damage the brain, kidneys, liver, and muscles. The faster you bring the temperature down, the better the outcome. Cold water immersion can drop core temperature roughly 1°C every five minutes when the water is actively stirred. That means someone at a dangerous 42°C could reach a safe range in about 15 minutes with proper cooling.
Immediate Cooling Steps
The gold standard is whole-body cold water immersion. Submerge the person from the neck down in cold water, anywhere from 1°C to 26°C (about 34°F to 79°F). If you have a tub, a stock tank, a kiddie pool, or even a tarp lined with ice water, use it. Stir the water continuously around the person to prevent a warm layer from forming against their skin.
If immersion isn’t available, the Wilderness Medical Society recommends evaporative cooling as the next best option: remove or loosen clothing, douse the person’s entire body with cold water so all skin is wet, and fan them aggressively. This method works at roughly half the speed of immersion but is far easier to set up in the field. Other alternatives include ice sheets, cold wet towels rotated frequently, and commercial ice packs placed on the neck, armpits, and groin.
At minimum, move the person to shade or an air-conditioned space. Passive cooling alone won’t reverse heat stroke, but it’s an essential first step while you prepare active cooling. Call emergency services immediately, but don’t wait for them to arrive before starting to cool.
When to Stop Cooling
Active cooling is typically stopped once core body temperature drops to about 38°C (100.4°F). Going lower risks overcorrection into hypothermia, since the body continues cooling even after you stop the intervention. In a field setting without a rectal thermometer (the only reliable method for core temperature), keep cooling until the person becomes more alert, stops being confused, or emergency medical personnel take over. Close monitoring should continue even after cooling stops, because temperature can rebound.
What Not to Do
Don’t give aspirin or acetaminophen. Heat stroke isn’t a fever, and these drugs won’t help. Aspirin impairs the blood vessels near the skin from dilating, which actually reduces the body’s ability to release heat. Acetaminophen poses a direct risk because heat stroke can injure the liver, and the drug is processed through the liver, compounding the damage. Don’t give alcohol. Don’t put the person in an ice bath and leave them unattended. And don’t delay cooling to drive to a hospital.
Hospital Treatment
Once in an emergency department, medical teams continue aggressive cooling if the core temperature is still elevated. They also begin IV fluids to restore blood volume and protect the kidneys. Heat stroke can cause muscle tissue to break down, a condition called rhabdomyolysis, which floods the bloodstream with proteins that can clog and damage the kidneys. Aggressive hydration is the cornerstone of preventing kidney failure from this process. Medical staff monitor urine output closely to track kidney function in real time.
In severe cases, heat stroke triggers a cascade of complications. The blood’s clotting system can malfunction, potassium levels can spike dangerously, and compartment pressure in the limbs can build to the point of requiring surgical release. These are intensive care scenarios that require blood products, dialysis, and close monitoring over days. The severity of these complications correlates directly with how long the person stayed at a critically high temperature before cooling began.
Recovery Timeline
After a heat stroke episode, the body needs significant time to recover. Physical activity should be avoided for at least one week, and the return to exercise or work in hot environments should be gradual and supervised. Some people experience temporary changes in heat tolerance, meaning they overheat more easily for weeks or months afterward. In a smaller number of cases, this increased sensitivity to heat becomes permanent.
Recovery from mild heat stroke with rapid cooling can take a few days to a couple of weeks. Recovery from severe heat stroke with organ involvement can take much longer, sometimes months, depending on which organs were affected and how extensively. People who experienced confusion, seizures, or prolonged loss of consciousness during the episode may need follow-up neurological evaluation, since the brain is one of the organs most vulnerable to heat damage.