Excessive Underarm Sweating

Excessive underarm (axillary) sweating is one of the most embarrassing forms of hyperhidrosis. It produces a thick, yellowish sweat that leaves a pungent odor and visible stains on clothing.

The Source of the Odor

Underarm sweat is different than that produced in most other areas of the body. The underarms have two types of sweat glands: eccrine glands, which are found all over the body, and apocrine glands, which are located only in the armpits and the groin.

Apocrine glands begin to develop at puberty. The sweat they produce contains proteins and fatty acids, which have a yellowish hue (the source of the yellowish stains on clothes.) The sweat has no odor—until the bacteria on skin and hair metabolize its protein and fatty acids. Once that process starts, the odor can be quite unpleasant.

A Tale of Two Glands

Although the apocrine glands are the source of underarm odor, it’s the eccrine glands that are responsible for the excessive sweating. That’s because eccrine glands get their messages from the nerve fibers of the sympathetic nervous system—the system that goes awry with hyperhidrosis. Apocrine glands, on the other hand, are regulated by hormonal processes.

Stopping Sweaty Underarms

Several treatments are available for axillary hyperhidrosis. These include oral anticholinergic medications and Botox injections, which can minimize the sweating for as long as 7 months. Both treatments work by blocking nerve messages that overactivate the eccrine sweat glands.

Another temporary treatment is iontophoresis, which uses a mild electrical shock to shut down the sweat glands.

A more permanent solution is surgery, including tumescent liposuction, which removes the eccrine sweat glands, and endoscopic thoracic sympathectomy, which snips the nerves that transmit messages to the glands. But surgery has risks, and is therefore only recommended as a last resort.