Heat rash appears as a red or pink rash consisting of small dots or pimple-like bumps, according to WebMD. The rash is often uncomfortable and itchy. Heat rash most often appears on the head, neck and shoulders in young children. Adults may notice the rash appearing on parts of the body covered by clothing. It may also appear between folds of skin, notes Mayo Clinic.
Heat rash occurs when sweat ducts become blocked and trap perspiration, explains Mayo Clinic. The severity of the heat rash can affect the type and severity of symptoms that accompany the rash. Mild heat rash only affects the top layer of skin and forms fluid-filled, blister-type bumps. When the condition affects the sweat ducts deeper in the skin, it often causes itchy red bumps that may cause a prickly feeling. When the heat rash affects the deep dermis layer, the sweat may leak out of the glands and into the skin where it forms firm lesions.
In general, the heat rash goes away on its own once the person gets out of the heat and cools the skin, says Mayo Clinic. Heat rash that reaches deeper into the skin sometimes becomes infected, causing inflammation and pus development. If the heat rash does not clear in a few days, oozes pus, comes with fever, causes swollen lymph nodes or increases in pain and redness, medical attention may be necessary.