Heat rash results when the body overheats and the sweat ducts get blocked and swell. These are common in children, however, adults may also experience them especially in hot and humid climates. Overview. Heat rash (miliaria rubra), also known as prickly heat, is a rash of small red bumps caused by blockage of the sweat glands. It can be due to high fever, excessive sweating, or being over-bundled. One of the best home remedies for heat rash is ice, followed up by a tepid powdered bath. If the heat rash is particularly severe.