Curriculum · ENT, Ophthalmology, and Dermatology
Miliaria
What it is
Miliaria, written as miliaria rubra and known more commonly as prickly heat or heat rash, is an inflammation of the sweat ducts. It is an acute inflammatory disorder of the skin that occurs in tropical climates, which also lends it the term lichen tropicus. It occurs because of sweat gland blockage and staphylococcal infection, and its acute phase is noted by vesicular lesions caused by obstruction of the sweat glands. It belongs with the other heat illnesses that follow a hot environment, such as heat edema and heat cramp.
Causes and risk
Heat illness comes of heat stress. The physiological responses to heat stress are decreased heat production, vasodilation and increased sweating. In the pathophysiology of heat illness itself the core temperature rises and blood is shunted from the splanchnic circulation to the skin and muscles. The risk factors are extremes of age, dehydration, poor physical condition and lack of acclimatization, obesity, lack of air-conditioning, diabetes, cardiovascular disease, alcohol abuse, and drugs such as diuretics, anticholinergics, sympathomimetics and salicylates. Exertional heat illness occurs in young, otherwise healthy individuals who take heavy exercise while ambient temperature and humidity are high, while the classic form occurs in elderly people whose chronic conditions impair thermoregulation or whose access to hydration or cooling is limited.