Miliaria is also called heat rash or sweat rash. It can develop anywhere on the body but is typically found on areas that have friction where heat and moisture are trapped, such as the neck, groins and armpits. In contrast to acne or folliculitis, miliaria develops around sweat glands and not near hair follicles.
It develops as multiple small 1-2 mm bumps when sweat glands are blocked. There are 3 main types of miliaria, categorized according to the depth of skin at which the sweat glands are blocked:
- Miliaria crystallina (also known as miliaria sudamina): sweat ducts are blocked just below the skin surface (stratum corneum). The rash appears as small clear blisters that break easily.
- Miliaria rubra (also known as prickly heat): sweat ducts are blocked in the upper skin layer called the epidermis. The rash appears as multiple very itchy small red bumps.
- Miliaria profunda: sweat glands are blocked in the middle layer of the skin called the dermis, causing red, deep, painful, itchy bumps.
A fourth type is called miliaria pustulosa, where bumps filled with pus form in miliaria lesions that are inflamed or infected by bacteria.
Humidity, warm temperature, and friction from clothing can all cause blockage of the sweat glands form miliaria. Bacteria that normally live on the skin, such as Staphylococcus epidermidis, produce a sticky substance that blocks the sweat ducts. Sweat then leaks outside of the sweat glands and causes skin irritation and inflammation. Miliaria is most common during humid summer months. It can also develop in the winter when people turn up the heater too high or wear too much clothing. Babies and patients who are hospitalized lay on their backs for a long period of time, and therefore are more likely to get miliaria.
- Steroids: Topical steroids may be used to help with itching and skin inflammation.
- Antiibotics: Topical or oral antibiotics may be needed to treat infected miliaria.
- Cool compresses: wet towels may help sooth inflamed miliaria.
- Lotions: Calamine or methanol lotion may help to soothe the skin.
- Prevent sweating: open the window to let air circulate. Turn down the heater or wear less clothing.
- Prevent skin irritation: wear loose, soft clothing made of breathable material or cotton.