Miliaria ("sweat rash", "heat rash" or "prickly heat") is a skin disease marked by small and itchy rashes. Miliaria is a common ailment in hot and humid conditions, such as in the tropics and during the summer season. The most commonly encountered form of the illness is miliaria rubra, in which obstruction causes leakage of sweat into the deeper layers of the epidermis, provoking a local inflammatory reaction and giving rise to the typical appearance of redness (hence rubra) and larger (but still only a few millimetres), blister-like lesions. This form of the illness is often accompanied by the typical symptoms—intense itching or "pins and needles" with a lack of sweating (anhidrosis) to affected areas.
Besides occlusion of sweat ducts, what are other possible causes of heat-induced, non-itchy, needle-prickling sensation all over the body that does not produce any visible rashes? And how can they be treated?
