Miliaria, an inflammatory disorder of human skin, characterized by multiple small lesions at the site of sweat pores, brought about by the blockage of sweat ducts and the resulting escape of sweat into various levels of the skin. Most cases of miliaria occur in extremely hot weather; the lesions tend to disappear with cooler weather and the resultant decrease in sweating.
Miliaria affects all ages and races and doesn’t discriminate between men and women. It’s most common in children, especially neonates; their sweat ducts haven’t fully matured yet. The condition is often the reason for dermatologic consults in hospitalized patients who spend a lot of time in bed, under blankets.
Types
- Miliaria crystallina is ductal obstruction in the uppermost epidermis, with retention of sweat subcorneally. It causes clear, droplike vesicles that rupture with light pressure.
- Miliaria rubra (prickly heat) is ductal obstruction in the mid-epidermis with retention of sweat in the epidermis and dermis. It causes irritated, pruritic papules (prickling).
- Miliaria pustulosa is similar to miliaria rubra but manifests as pustules rather than papules.
- Miliaria profunda is ductal obstruction at the entrance of the duct into the dermal papillae at the dermo-epidermal junction, with retention of sweat in the dermis. It causes papules that are larger and more deeply seated than those of miliaria rubra. Papules are frequently painful.
Miliaria is most common in the first few weeks of life. It is especially common in hot, humid weather but almost any baby can get it. It is more common in babies who are bundled too warmly. Older children and adults can also get miliaria, in which case it is often called “prickly heat.”
Causes
Heat rash develops when some of your sweat ducts clog. Instead of evaporating, perspiration gets trapped beneath the skin, causing inflammation and rash. It’s not always clear why the sweat ducts become blocked, but certain factors seem to play a role, including –
- Immature sweat ducts – A newborn’s sweat ducts aren’t fully developed. They can rupture more easily, trapping perspiration beneath the skin. Heat rash can develop in the first week of life, especially if the infant is being warmed in an incubator, is dressed too warmly or has a fever.
- Tropical climates – Hot, humid weather can cause heat rash.
- Physical activity – Intense exercise, hard work or any activity that causes people to sweat heavily can lead to heat rash.
- Overheating – Overheating in general — dressing too warmly or sleeping under an electric blanket — can lead to heat rash.
- Prolonged bed rest – Heat rash can also occur in people who are confined to bed for long periods, especially if they have a fever.
Risk Factors
- Age – Newborns are most susceptible.
- Tropical climates – People living in the tropics are far more likely to have heat rash than are people in temperate climates.
- Physical activity – Anything that makes people sweat heavily, especially if people are not wearing clothing that allows the sweat to evaporate, can trigger heat rash
Symptoms
The following are the most common symptoms of prickly heat. However, each individual may experience symptoms differently. Symptoms may include –
- Itching
- Irritation (prickling)
- Small blisters
- Large, red areas on skin
The symptoms of prickly heat may resemble other skin conditions. Always consult your doctor for a diagnosis.
Complications
Heat rash usually heals without problems, but it can lead to infection with bacteria, causing inflamed and itchy pustules.
Treatment
Avoid further sweating – Even if this is achieved for only a few hours a day, as in an air-conditioned office or bedroom, considerable relief is experienced. For the very susceptible person a move away from tropical climates may be essential.
Do not irritate the skin – Avoidance of excessive clothing, friction from clothing, excesssive soap and contact of the skin with irritants will reduce the liability to miliaria. Shirts and blouses should be made of the new breathable synthetic fabrics where available, otherwise of cotton.
Cool water compresses and good ventilation will soothe inflamed areas.
Calamine lotion – Calamine is probably as effective as anything for relief of discomfort, but because of its drying effect an emollient may subsequently be required.
Topical steroids – For more marked cases, mild topical steroids often give reasonable relief of symptoms while natural resolution of the condition is awaited.
Antiseptics – Antiseptics and antistaphylococcal antibiotics can combat bacterial overgrowth.
Reference –
http://www.hopkinsmedicine.org/healthlibrary/conditions/dermatology/prickly_heat_85,P00307/
http://familydoctor.org/familydoctor/en/diseases-conditions/heat-rash/symptoms.html
http://www.msdmanuals.com/professional/dermatologic-disorders/sweating-disorders/miliaria
http://www.britannica.com/science/miliaria
http://www.drgreene.com/articles/miliaria/
http://www.whattoexpect.com/first-year/baby-care/baby-skin-care/heat-rash.aspx