April 16, 2007

Sweating Disorders


Sweat is made by sweat glands in the skin and carried to the skin's surface by ducts. Sweating helps keep the body cool. Thus, people sweat more when it is warm. They also sweat when they are nervous, under stress, or exercising.

Sweat is composed mostly of water, but it also contains salt (mostly sodium chloride) and other chemicals. When a person sweats a lot, the lost salt and water must be replaced

Excessive Sweating
People with excessive sweating (hyperhidrosis) sweat profusely, and some sweat almost constantly. Although people with a fever or those exposed to very warm environments sweat, people with excessive sweating tend to sweat even without these circumstances. Excessive sweating may affect the entire surface of the skin, but often it is limited to the palms of the hands, soles of the feet, armpits, or genital area.

Usually, no specific cause is found. However, medical disorders that can cause excessive sweating include hyperthyroidism, a low level of sugar in the blood, and, rarely, pheochromocytoma. An abnormality in the part of the nervous system that controls sweating can cause excessive sweating as well. Also, people with a spinal cord injury or disease may have episodes of excessive sweating. People with excessive sweating are frequently anxious about their condition. This anxiety often makes the sweating worse.

Severe, chronic wetness can make the affected area white, wrinkled, and cracked. Sometimes the area becomes red and inflamed. The area may emit a foul odor (bromhidrosis) due to the breakdown of sweat by bacteria and yeasts that normally live on the skin.


Excessive sweating can be controlled to some degree with commercial antiperspirants. However, stronger treatment is often needed, especially for the palms of the hands, soles of the feet, armpits, or genital area. Nighttime application of aluminum chloride solution may help; prescription and nonprescription strengths of this drug are available. A person first dries the sweaty area and then applies the solution. If the response is inadequate, a plastic film can be applied over the solution to enhance the effectiveness of the treatment. In the morning, the person removes the film and washes the area. Some people need two applications daily; this regimen usually gives relief in a week. If the solution irritates the skin, the plastic film should be left off.

A solution of methenamine also may help. Tap water iontophoresis, a process in which a weak electrical current is applied to the sweaty area, is sometimes used. Drugs taken by mouth, such as phenoxybenzamine and propantheline, sometimes control sweating, and injections of botulinum toxin into the affected area diminish sweating. If drugs are not effective, a more drastic measure to control severe sweating is surgical cutting of the nerves leading to the sweat glands. Excessive sweating limited to the armpits is sometimes treated by liposuction to remove the sweat glands. Psychologic counseling or antianxiety drugs may relieve sweating caused by anxiety.

For the few people in whom odor is a problem, cleansing twice daily with soap and water usually removes the bacteria and yeast that cause odor. In some people, a few days of washing with an antiseptic soap, which may be combined with use of antibacterial creams containing clindamycin or erythromycin, may be necessary. Shaving the hair in the armpits may also help control odor.

Prickly Heat
Prickly heat (miliaria) is an itchy skin rash caused by trapped sweat.

Prickly heat develops when the narrow ducts carrying sweat to the skin surface get clogged. The trapped sweat causes inflammation, which produces irritation (prickling), itching, and a rash of very tiny blisters. Prickly heat also can appear as large, reddened areas of skin.

Prickly heat is most common in warm, humid climates. It tends to occur on areas of the body where skin touches skin, such as under the breasts, on the inner thighs, and under the arms.

The condition is controlled by keeping the skin cool and dry. Use of powders and antiperspirants often helps. Conditions that increase sweating should be avoided; an air-conditioned environment is ideal.

Adapted from: Merck & Co. Inc.