Q&A: What causes heat rash? | Expert Opinion - The Philadelphia Inquirer
As sweat evaporates off the skin, it cools our bodies under hot conditions. When this process goes awry, heat rash can develop. Heat rash occurs when excessive sweat clogs sweat glands, trapping perspiration. As sweat builds up within the sweat glands, small clear blisters start to show on the skin. Sweat then leaks out from the gland into the surrounding skin, causing inflammation that appears as red bumps on the skin's surface. Heat rash, also referred to as "prickly heat" and miliaria, affects people of all ages and genders, and frequently appears on newborns — often on the neck, chest, and back — due to immature sweat ducts. In adults, heat rash can be widespread. Because sweat cannot easily evaporate from skin folds, the condition frequently arises in the inner elbows, backs of the knees, under the breasts and abdomen and in the groin. The risk of developing heat rash increases with exposure to tropical climates, increased physical activity, overheating, severe ...