Harvard Health Letters

Excessive sweating, or hyperhidrosis, can take a serious toll, making handshakes unpleasant, intimacy difficult, and some types of work impossible. People with hyperhidrosis may have to change their blouses or shirts two or three times a day. Although the underarms, palms, feet, and groin are most often involved, any part of the body may be affected. The condition is also associated with certain skin problems, including atopic dermatitis. And it's not rare; 2 percent to 3 percent of the population suffers from hyperhidrosis.

Acetylcholine is a neurotransmitter that activates sweat glands. Botox blocks the release of acetylcholine in the nerve ending, preventing the nerve cell from communicating with the sweat gland.

NORMAL SWEATING

The body has two types of sweat glands, eccrine and apocrine. The eccrine sweat glands are thought to be responsible for hyperhidrosis. The main function of eccrine sweat glands is thermoregulation, with cooling resulting from the evaporation of eccrine sweat. (The role of apocrine sweat glands is less well understood.) This process is controlled by the sympathetic nervous system, which orchestrates the "fight or flight" response -- the body's reaction to emergencies and other forms of stress. The sympathetic nervous system activates the eccrine glands through the chemical messenger acetylcholine. People with hyperhidrosis are hypersensitive to this signal, so they produce several times more eccrine sweat than average. Hyperhidrosis seems to run in families, but we know little about its causes.

Hyperhidrosis is not the only possible explanation for excessive sweating. Others include cancer, infections, hormonal or metabolic imbalances, and certain neurological conditions. Some medications can also cause sweating. To determine the actual reason, see a clinician.

TREATING EXCESSIVE SWEATING

In most cases, excessive sweating isn't dangerous; it's simply embarrassing and inconvenient. But that's reason enough to want to do something about it. Deodorants help by reducing odor but they don't affect sweating. Treatments for hyperhidrosis include:

1. Topical antiperspirants.

This is the first choice for underarm sweating and is also effective on hands and feet. Look for a preparation containing an aluminum salt, such as aluminum chloride. The aluminum salt irritates the sweat gland, which swells and prevents the sweat from exiting. The more of the salt the antiperspirant contains, the longer it will work. People with hyperhidrosis generally need antiperspirants containing 10 percent to 20 percent aluminum salts. Over-the-counter preparations come in various strengths, and one may work for you. If not, you can try a prescription-strength preparation, such as aluminum chloride hexahydrate (Drysol, others). You apply it to dry skin at night once or twice a week, and you may have to sleep with plastic wrap over your armpits, or with plastic wrap and gloves or socks on the hands or feet. The main side effect is local irritation.

2. Iontophoresis.

This procedure has been used for more than 60 years to treat excessive sweating on the hands or feet (and, more recently, in the underarm). Your hands or feet are submerged in lukewarm tap water for 20 to 30 minutes while a mild electric current -- just enough to cause a tingling sensation in the hands or feet -- is passed through the water. Experts don't know exactly how it works but it appears to temporarily block sweat glands. Sweating usually improves after five to 10 sessions at the rate of three or four sessions per week. You may need one to three sessions per week thereafter to maintain sweat relief. The main side effect is dry or irritated skin. FDA-approved equipment is available for home use, although it may not be covered by insurance. Iontophoresis is not an option if you're pregnant or have a cardiac pacemaker or a metal orthopedic implant.

3. Botulinum toxin.

Botulinum toxin A (Botox) injections are FDA-approved for treating underarm hyperhidrosis and are also effective for hands and feet. Multiple injections are required; for example, a typical underarm treatment involves 12 to 14 injections for each armpit. Botox works by blocking the release of acetylcholine from nerve cells. Complete relief usually comes within a day or two, and the effect lasts for six to 10 months. Injections into the palms and soles can be painful; those in the armpits, less so. Risks include bleeding at the injection site and muscle weakness in the hands. The cost -- about $1,000 for treating both armpits -- may or may not be covered by insurance.

4. Medications.

Some clinicians prescribe oral anticholinergic medications (drugs that reduce the activity of acetylcholine). But acetylcholine has many functions in the body, and these drugs are systemic, meaning they don't affect the sweat glands alone. To reduce sweating, you have to take anticholinergic medications at a dose that usually causes some undesirable side effects, including dry mouth, impaired taste, blurred vision, and urinary retention. This form of treatment for hyperhidrosis hasn't been approved by the FDA.

5. Surgery.

A few patients may need surgery to remove the affected sweat glands -- sometimes with minimally invasive techniques such as liposuction -- or to cut the nerves that activate the glands. This latter procedure, performed under anesthesia, is called endoscopic thoracic sympathectomy (ETS). It works best for sweaty palms. Possible side effects include excessive sweating in other parts of the body (called compensatory sweating) as well as lung and nerve problems. You should not consider surgery unless the problem is serious and all other options have been exhausted. - Harvard Women's Health Watch

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