Miliaria (Heat Rash)

Miliaria, also called heat rash, sweat rash or prickly heat, is a skin eruption caused by blocked eccrine sweat ducts. Sweat that cannot reach the skin surface leaks into the surrounding skin and forms small blisters or bumps, sometimes with inflammation and itching. The underlying problem is trapped sweat. Uncomplicated miliaria is not an infection and is not contagious, so isolation is not needed for the rash itself. The depth of the blockage determines the type. In miliaria crystallina the obstruction is in the uppermost layer of the epidermis, so the blisters are clear, very superficial and break easily. In miliaria rubra (prickly heat) the blockage is in the mid-epidermis, producing red, itchy papules. Miliaria pustulosa is a variant of miliaria rubra in which the lesions are pustules. In miliaria profunda the blockage is deeper, where the duct enters the dermis, producing firm, deeper, skin-coloured papules. Risk factors are anything that increases sweating or stops sweat from evaporating: hot and humid weather, fever, intense exercise, overdressing or heavy wrapping, synthetic or non-breathable clothing, non-porous dressings, and prolonged bed rest on...