Miliaria crystalline
The most superficial obstruction (with the most mild clinical presentation), is known as miliaria crystalline; instead of a rash, the patient presents with multiple, tiny, blister-like lesions that look like beads of perspiration and essentially cause no symptoms. : 23  Miliaria crystalline is also known as miliaria crystallina, and sudamina. The superficial vesicles are not associated with an inflammatory reaction. : 23

Miliaria rubra
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. : 23  A small risk of heat exhaustion exists due to inability to sweat if the rash affects a large proportion of the bodys surface area or the patient continues to engage in heat-producing activity. Miliaria rubra is also known as prickly heat and heat rash. Differential diagnosis should be used to rule out polycythemia vera, which is a rare hematological disorder and appears more often in males than females, generally not before the age of 40. Both disorders share a common trait of appearing after taking a hot shower.
General measures should be recommended for all patients, including moving to an air-conditioned environment if possible, avoiding sweat-provoking activities and occlusive clothing, and taking frequent, cool showers. The use of topical antibacterials (including antibacterial soaps) may shorten the duration of symptoms in miliaria rubra even in the absence of obvious superinfection. Other topical agents that may reduce the severity of symptoms include anti-itch preparations such as calamine or menthol- or camphor-based preparations, and topical steroid creams. Caution should be used, however, with oil-based preparations (ointments and oily creams as opposed to water-based or aqueous lotions) that may increase blockage of the sweat glands and prolong the duration of illness. Other agents have been investigated including supplemental vitamin A and C and vitamin A based medications, but little scientific evidence supports any of the above treatments in reducing the duration of symptoms or frequency of complications. In most tropical areas, the local dispensaries sell prickly heat powder, a talc admixture containing drying milk proteins (labilin) and Triclosan to fight bacterial infection. These include cooling menthol to help alleviate difficulty getting to sleep. This is an effective treatment; the powder stays on the skin longer and treats bacteria dispersed into bed linens, providing a reasonably dry refuge area for healing. Miliaria often covers large areas, and generous use of cortisone may be contraindicated for reasons stated on package warnings. Regular talcum powder does not reduce the rash, but can alleviate burning and itching.