What causes heat stroke?

Summer temperatures in the United States can climb above100 degrees Fahrenheit(38 degrees Celsius), making heat stroke a big problem. Heat stroke can be fatal in many cases because it happens so quickly -- there is not much time to react.

Let's say that it really is 100 degrees F outside. The human body wants to stay at98.6 degrees F. The only way to stay at 98.6 is tosweat. By putting moisture on the skin and letting it evaporate, your body can cool itself very effectively and keep its temperature in the proper range.

Sweat works really well as long as there is plenty ofwaterin your body -- it takes water to manufacture sweat. If you run out of water, sweat stops and your body rapidly overheats. It turns out that it is extremely easy to run out of water -- your body can produce 0.5 gallons (2 liters) of sweat every hour in a hot environment. Unless you are drinking water at the same rate, you willdehydrateand thenstop sweating. Your internal thirst meter often is not sensitive enough when you need that much water (and it has been said that by the time you feel thirsty, you're already dehydrated), so you have to keep drinking regardless of how thirsty you feel.

The other thing that can lead to heat stroke is veryhigh humidity, which keeps sweat from evaporating.

In either case -- be it the lack of sweat or the inability to evaporate it -- the core body temperature can rise very quickly if it is hot outside. Once the core gets to106 degrees F, it is a serious problem. Symptoms include red, hot, dry skin (the body dilates skinblood vesselsto try to release heat, making the skin red, and the dryness comes from lack of sweat), rapidheartrate, dizziness and confusion. The dizziness and confusion come from the high body temperature, which affects thebrain.

Forchildrenand宠物, one way for heat stroke to happen suddenly and unexpectedly involves a hot car or a hot room in a house. Cars are especially dangerous. AtHowStuffWorkswe did the following experiment:

Within 15 minutes, the interior temperature of the car was110 degrees F. This temperature is quickly fatal.

The reason the temperature rises so high and so fast is because the interior of a car is an excellent solar oven that uses thegreenhouse effectto trap heat. Sunlight heats the sheet metal of the car, and it streams in through the windows to heat the interior. It turns out that glass is completely transparent tovisible lightbut opaque to infrared light -- and infrared light is the heat that is trying to radiate back out of the interior. So the temperature rises rapidly, to the point where you often cannot touch thesteering wheelwithout getting singed. Leaving the window cracked is not going to help -- it is never safe to leave a child or pet in a parked car for any length of time.

The only solution for heat stroke is tocool the persondown. You can:

If not treated, heat stroke can be fatal in less than an hour.