Understanding Heat Rash - the Basics

What Is Heat Rash?

Heat rash -- also called prickly heat or miliaria -- is a common condition in which areas of the skin itch intensely and often feel prickly or sting due to overheating. Heat rash looks like tiny bumps surrounded by a zone of red skin. It usually occurs on clothed parts of the body, such as the back, abdomen, neck, upper chest, groin, or armpits and goes away on its own within a few days. In severe forms, however, heat rash can interfere with the body's heat-regulating mechanism and cause fever, heat exhaustion, and even death.

Heat rash occurs most often in hot, humid conditions. It's most common in infants. Active people, newborns in incubators, and bedridden patients with fever also are more likely to get heat rash.

What Causes It?

Heat rash begins with excessive perspiration, usually in a hot, humid environment. The perspiration damages cells on the surface of the skin, forming a barrier and trapping sweat beneath the skin, where it builds up, causing the characteristic bumps. As the bumps burst and sweat is released, you may feel the prickly, or stinging, sensation that gives this condition its common name.