The skin’s job is to protect the inside of the body from the outside world. 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 can’t get to the surface of the skin. Instead, it becomes trapped beneath the skin’s surface causing a mild inflammation or rash.
Heat rash is also called prickly heat or miliaria.
Heat rash facts
- Heat rash occurs when the skin’s sweat glands are blocked and the sweat produced cannot get to the surface of the skin to evaporate. This causes inflammation that results in a rash.
- The rash appears as reddened skin with tiny blisters and is due to inflammation. It often occurs in skin creases or areas of tight clothing where air cannot circulate.
- The rash may be itchy or cause a prickly sensation and therefore it is also known as prickly heat.
- Heat rash usually fades when the skin is allowed to cool. Medical treatment is necessary only if the area becomes infected.
- Heat rash can be prevented by avoiding hot, humid conditions, wearing lose fitting clothes and using air conditioning or fans to allow air to circulate.
What are the causes of heat rash?
It is uncertain 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 wintertime or when chilled because of an illness with fever.
- Heavy creams or lotions can clog sweat ducts.
Babies have immature sweat glands that aren’t able to 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 occur as a side effect of some medications (for example, isotretinoin [Accutane] or clonidine [Catapres]).
What are the symptoms of heat rash in children and adults?
The common symptoms of heat rash 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 can’t complain about the rash sensation, he or she may be fussy.
Credit – Charles Patrick Davis, MD, PhD – 5/20/2013 (MedicineNet.com)