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Sudamina, or miliaria crystallina, is a form of heat or sweat rash. The rash is caused by blocked sweat ducts that keep the sweat trapped under the skin, causing a reaction. Infants are more likely to suffer from sudamina than older children and adults, because their sweat glands are not fully developed, making them more likely to rupture or become blocked. Rash symptoms usually appear in skin folds or areas where clothing is tight and rubs against the skin, such as the armpits, elbows, neck, chest, and groin.
The most common symptom of sudamina is small, clear blisters that rupture easily with pressure or friction. This is the most mild form of heat rash and does not usually cause serious complications. While the blisters may be irritating, they are not usually painful or itchy. The condition usually occurs when people are outside in hot, humid weather or are participating in activities that stimulate excessive perspiration, such as playing sports.
Treatment for sudamina is usually as simple as allowing the skin to breathe to reduce the amount of perspiration trapped against the skin. Removing clothing from affected areas and moving to a cooler environment are the best ways to reduce sweat. Once the heat source is removed and the person stops sweating, the rash usually goes away quickly. Though the blisters break open easily, people with sudamina should not pop them on purpose.
It is important for people with sweat rashes to wash their skin with cool water and a mild antibacterial soap after the rash has cleared. The small openings created when the blisters pop make the skin susceptible to infection from germs and bacteria in the environment. Allowing the skin to air dry after washing can help prevent irritation of the sensitive skin.
Most cases of sudamina can be prevented by wearing loose clothes made from breathable fabrics, such as cotton, when spending long periods in hot weather or engaging in strenuous exercise. Placing newborns in front of a fan or cool breeze can also help prevent the rash. Before going outside or exercising, people prone to heat rash should avoid applying heavy creams or lotions. These products increase the risk of blocked sweat ducts.
People who have recurring problems with sweat rashes should talk to their doctors about other possible contributing factors. Certain medications can affect the sweat ducts and may make people who take them more prone to heat rash. Changing to another medication or altering the dosage may help alleviate these problems. Common medications that may cause heat rash include clonidine, isotretinoin, and bethanechol.