Miliaria Rubra (Heat Rash)

What is Miliaria Rubra?

A type of heat rash called Miliaria Rubra, which can also be known as prickly heat, causes small red bumps that may itch or be irritating. The sweat glands become blocked and cannot work properly, leading to skin irritation. Friction can exacerbate the rash, so body parts that touch or rub together such as between the legs or under the arms are most likely to be affected.

Most cases of miliaria rubra occur in warmer or humid climates, and are most likely to happen to people who are not used to this type of environment. Excessive sweating or over-bundling can make you more vulnerable. Anyone can get heat rash, but Asian people are slightly less likely to get this form of the rash.

Very young children who are overdressed are susceptible to heat rash, because caregivers are often concerned that they be kept warm enough.

What are the Symptoms of Miliaria Rubra?

The most obvious sign of heat rash are the small, red bumps that it causes. These can appear on any area of the body, but most commonly on areas with friction, including body folds. Most people who suffer from heat rash do not get the bumps on their faces, hands or soles of the feet.

The bumps may become itchy or may sting or feel prickly, and this sensation becomes worse if you become overheated again.

Heat rash can also cause you to become easily tired and have difficulties coping with the heat. You may also stop sweating or sweat less, especially in the affected areas.

Miliaria Rubra (Heat Rash) Causes

Miliaria Rubra (Heat Rash) is the result of a blockage in sweat ducts. When you perspire, sweat travels from glands just beneath the surface of the skin, through sweat ducts, which then releases sweat through the pores. When the ducts are blocked, the sweat is left with no other option than to seep into the nearby skin, spreading to cause inflammation. In turn, the inflammation becomes the rash.

Research suggests that the Staphylococcus epidermidis bacteria plays a role in blocking sweat ducts. A substance produced by the bacterium works as an adhesive, combining with excess sweat and dead skin cells. This concoction may be what clogs the sweat ducts.

While people with miliaria are more prone to developing the rash, that’s not always the case. For instance, wearing skin-tight apparel, such as leggings made from polythene, can also block sweat ducts and produce the heat rash.

How is Miliaria Rubra Treated?

The best treatment for heat rash is to get to a cool, comfortable environment. Once you’re not overheated and your sweat glands are no longer blocked, your skin will recover. Bathing or showering in cool water with a non-drying soap can help to soothe the skin and clear the rash.

Calamine lotion or another ointment intended for mild rash can help resolve the itching and prickly feeling. Make sure you don’t choose a lotion or ointment that contains petroleum, as this can further block the sweat glands and make the rash worse.

For very severe cases of heat rash, your doctor may prescribe a topical steroid.

Miliaria Rubra (Heat Rash) Prevention

In preventing Miliaria Rubra, the key is to take actions to limit sweating and especially the overproduction of sweat. Reducing heat and humidity can go a long way towards achieving this goal. Additionally, treating a fever, removing tight-fitting clothing, and limiting physical exertion are all recommended methods of reducing the risk of developing heat rash. Air conditioning and moving to cooler climates may be other options to consider, particularly for patients who frequently experience Miliaria Rubra.

Skin treatments can both prevent and treat heat rash. This includes lotions and ointments containing calamine, boric acid, or menthol. Cold compresses and frequent showering with moisturizing bars can also help to reduce the risk and occurrence of heat rash. The use of regular body soap is discouraged, because it may dry out the skin. Where the heat rash is severe, a doctor may prescribe topical corticosteroids or topical antibiotics. Anhydrous lanolin has had significant success in reducing heat rash associated with miliaria profunda.

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Last Reviewed:
October 10, 2016
Last Updated:
March 08, 2018