Heat rash is sometimes called prickly heat or sweat rash. It's typically a harmless condition but causes severe itching on the skin. In this condition, a person will experience small red spots in places where most of the sweat collects. The most common areas are the armpits, back, chest, groin, elbow ceases and under the breasts. Heat rash is usually caused by excessive sweating, commonly in summer or hot climates. For same-day heat rash ...