The heat rash discomfort

CEBU, Philippines — Heat rash occurs when the skin's sweat glands are blocked and the sweat produced cannot get to the surface of the skin in order to evaporate. This causes inflammation that results in a rash.

Common symptoms of heat rash include red bumps on the skin, and a prickly or itchy feeling to the skin (also known as prickly heat). The rash appears as reddened skin with tiny blisters and is due to inflammation. It often occurs in skin creases or at areas of tight clothing where air cannot circulate.

Heat rash usually fades when the skin is allowed to cool. Medical treatment is necessary only if the area becomes infected.

The condition can be prevented by avoiding hot, humid conditions, wearing lose fitting clothes, and using air conditioning or fans to allow air to circulate.

The skin's job is to protect the inside of the body from the outside threats. It acts as a preventive barrier against intruders that cause infection, chemicals, or ultraviolet light from invading or damaging the body. It also plays an important role in the body's temperature control. One way that the body cools itself is by sweating, and allowing that sweat or perspiration to evaporate. Sweat is manufactured in sweat glands that line the entire body (except for a few small spots like fingernails, toenails, and the ear canal).

Sweat glands are located in the dermis or deep layer of the skin, and are regulated by the temperature control centers in the brain. Sweat from the gland gets to the surface of the skin by a duct.

A heat rash occurs when sweat ducts become clogged and the sweat cannot get to the surface of the skin. Instead, it becomes trapped beneath the skin's surface causing a mild inflammation or rash.

It defies explanation why some people get heat rashes and others don't.

The sweat gland ducts can become blocked if excessive sweating occurs, and that sweat is not allowed to evaporate from a specific area. Some examples of how blockage may occur include the following:

• Creases in the skin like the neck, armpit, or groin have skin touching adjacent skin, which makes it difficult for air to circulate, and prevents sweat evaporation;

• Tight clothing that prevents sweat evaporation;

• Bundling up in heavy clothing or sheets. This may occur when a person tries to keep warm in cold season or when chilled because of an illness with fever.

• Heavy creams or lotions can also clog sweat ducts;

• Babies have immature sweat glands that aren't able to efficiently remove the sweat they produce. They can develop heat rash if they are exposed to warm weather, are overdressed, excessively bundled, or have a fever.

Heat rash may also occur as a side effect of some medications (for example, clonidine like Catapres).

The common symptoms of heat rash, in both children and adults, are red bumps on the skin, and an itchy or prickly feeling to the skin. These are due to inflammation of the superficial layers of the skin (the epidermis) and the prickly sensation is similar to the feeling of mild sunburn.

The symptoms of heat rash are the same in infants and adults; however, since an infant cannot complain about the rash sensation, he or she may be simply become fussy.

Newborns, infants, the elderly, and obese individuals with large areas with skin-on-skin contact areas (for example, a large overlapping area of abdominal fat) are at risk for developing heat rash. They all are especially at risk if they are immobile for long periods and parts of the skin aren't exposed to circulating air, which results in the inability of the sweat ducts to "breathe" (evaporative cooling).

Heat rash is more common in places with hot, humid, climates because people sweat more.

Intense exercise associated with lots of sweating may cause a heat rash, especially if the clothing worn does not allow adequate air circulation.

Medical Editor: Charles Patrick Davis, MD, PhD