Heat rash is a common term for a number of skin problems that develop as a result of exposure to heat. Infants, elder people, and obese people are more prone to this condition, as they have more areas with skin-to-skin contact. This condition develops due to blockage of sweat ducts, which causes itching and development of a rash. Also known as prickly heat, this condition is more common in regions with hot and humid climate.