Heatstroke

Heat stroke is the most severe form of heat-related illness (hyperthermia). It occurs when your body overheats and can’t cool down. It can develop if you’re in a very warm space, like a home without air conditioning, or if you’re doing intense physical activity that generates lots of body heat. Heat stroke causes your body temperature to soar to dangerous levels, typically above 104 degrees Fahrenheit (40 degrees Celsius).

Untreated heat exhaustion (a moderate form of heat-related illness) can lead to heat stroke. But heat stroke can also develop without warning. Heat exhaustion and heat stroke share similar symptoms — like dizziness, nausea and weakness. But a key difference is that heat stroke causes brain dysfunction (encephalopathy). This means you experience changes to your thinking and behavior — like confusion, agitation and aggression. You may also pass out.

Heat stroke is life-threatening and requires immediate medical treatment. The longer your body temperature remains high, the greater your risk of complications (like organ damage) or death.

If you or someone around you has signs or symptoms of heat stroke, call 911 or your local emergency services number immediately.

Other names for heat stroke include:

• Sunstroke.
• Life-threatening hyperthermia.

Types of heat stroke

There are two types of heat stroke:

• Classic (non-exertional) heat stroke. Heat in your environment (like a car, home or outdoor space) overwhelms your body’s ability to cool itself. Classic heat stroke typically affects children and adults over age 65. This is the type you hear about on the news during heat waves.
• Exertional heat stroke. You generate lots of heat through physical activity (metabolic heat), and it’s more than your body can handle. Exertional heat stroke often occurs when physical activity and hot weather mix, but it can also occur in normal temperatures. This type of heat stroke typically affects young, healthy adults.