The Body's Response to Warm Temperatures

The body has different ways of ridding itself of excess heat. When the body is warmer than its surroundings, heat flows from warmer to cooler areas of the body, which promotes cooling. The body also produces moisture that cools the skin as it evaporates (sweating). Wearing tight or heavy clothing makes sweating less effective by preventing evaporation from the skin surface. Humidity (the presence of moisture in the air) also slows evaporation, making sweating less effective. For example, an air temperature of 90° F might be tolerable for many people if humidity is only 40%. But 90° F or even 80° F would be dangerous for many of those same people if the humidity were to rise to 80%. The body also gets rid of some heat through the evaporation that occurs during breathing, but this too is decreased by humidity. Getting rid of excess heat is therefore more difficult in hot, humid weather.

Older people in particular tend to have difficulty increasing the flow of blood to all skin surfaces. Certain drugs, such as antipsychotics and antidepressants, and some diseases that affect the skin, such as scleroderma and psoriasis, can also interfere with sweating. Other disorders, such as heart failure and obesity, can interfere with the body's ability to cool itself as well. Aging itself also affects thirst; older people do not get thirsty as readily as younger people. Thus, older people tend to get dehydrated, which in turn means they are less able to sweat in warm surroundings.

Back to Hyperthermia.