Sweating that exceeds the needs of the body—medically termed hyperhidrosis—is fairly common, affecting 1%–3% of the population. Hyperhidrosis may be generalized but most often it involves the palms, underarms, feet, and groin; it can take a social toll, making handshaking unpleasant and some handwork impossible.
We need sweating to control body temperature; water evaporating from the skin cools the body. Sweating is under the control of the sympathetic nervous system, which orchestrates the body's reaction to stressful situations and emergencies. The sympathetic nervous system activates the sweat glands through the chemical messenger acetylcholine. People with hyperhidrosis produce several times more sweat than normal because they are particularly sensitive to this signal. Hyperhidrosis seems to run in families, but we don't know much more about what causes it.
Generalized sweating could be a sign of a hormonal condition, infection, cancer, or anxiety disorder that requires treatment. To be sure, you should see your clinician. Most of the time, though, excessive sweating is not dangerous but simply embarrassing and inconvenient.
Hyperhidrosis can be treated in several ways. Topical antiperspirants are the first-line treatment for underarm sweating and are also effective on hands and feet. The best choice is a preparation containing aluminum salts, such as aluminum chloride. The aluminum salt irritates the sweat gland and causes it to swell, preventing the sweat from leaving. People who sweat excessively generally need antiperspirants with 10%–15% aluminum salts. These are applied at night once or twice a week and may require sleeping with the armpits wrapped in plastic wrap, or plastic wrap and gloves or socks on the hands or feet. The main side effect is local irritation.
A procedure called iontophoresis has been used for more than 50 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 10–20 minutes while a mild electric current is passed through the water. Apparently this temporarily blocks the sweat gland, although experts don't know exactly how it works. Sweating symptoms usually improve after 5–10 sessions at the rate of three or four sessions per week. Most people need one or two sessions per week thereafter to maintain sweat relief. The main side effect is dry or irritated skin. You should avoid iontophoresis if you are pregnant or have a cardiac pacemaker or a metal orthopedic implant.
Botulinum toxin (Botox) injections are FDA-approved for treating underarm hyperhidrosis. They have also been found effective for hands and feet and are the treatment of choice for marked hyperhidrosis. Multiple injections are required; a typical underarm treatment involves 12–14 injections per armpit. Botox appears to work by temporarily paralyzing the nerves that release acetylcholine. Patients notice complete relief within a day or two, and the effects last 6–10 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.
Some doctors prescribe oral anticholinergic medications (drugs that reduce the activity of acetylcholine) to curb the sweat glands, but this approach is not approved by the FDA. Anticholinergic medications can cause some undesirable side effects, such as dry mouth, constipation, impaired taste, blurred vision, and heart palpitations.
In severe cases, surgery can be performed to cut the sympathetic nerves to the sweat glands (sympathectomy). Sympathectomy works best for sweaty palms.
To learn more
You can read more about hyperhidrosis at www.sweathelp.com, the Web site for the International Hyperhidrosis Society.