Heat rash, also known as miliaria or prickly heat, is when the skin develops a prickly or stinging sensation after overheating. It occurs most often in hot and humid climates. Those who are most likely to experience heat rash include infants in incubators, active people and bedridden people with fevers.

Heat rash starts with excessive sweating that causes the ducts in the sweat glands to become blocked. The sweat then moves into surrounding tissue and irritates the skin. The rash appears as tiny bumps surrounded by red skin. Heat rash typically appears on skin that is covered by clothes and in skin folds that cause friction. This includes the abdomen, neck, back, groin, chest and armpits. Normally the rash will clear up when the skin cools off.

There are four types of heat rash. The mildest form is miliaria crystallina which affects the sweat ducts within the top layer of skin. Clear, fluid-filled blisters that open easily will appear. The next type is miliaria rubra. This causes red bumps, itching and prickling. The third type is miliaria pustulosa, which is when the sacs of fluid inflame with pus. The last and least common type of heat rash is miliaria profunda. This affects a deep layer of skin (dermis), and causes sweat to leak and form flesh-colored lesions that look similar to goose bumps.

If heat rash is severe and you notice more pain, swelling, swollen lymph nodes, fever, warmth or draining pus, contact your physician.  Make sure to stay hydrated and wear sunscreen during the hot summer days! Also, be sure to wear and deodorant to prevent sweating and take breaks in the shade or air conditioning to cool down. Don’t overheat yourself and your skin!