There is more to Botox than the dewrinkling of pretty faces. The FDA originally approved botulinum toxin type A in 1989 for the treatment of two types of eye-muscle problems — uncontrollable blinking (blepharospasm) and misaligned eyes (strabismus), including crossed eyes. Since then, doctors have used injections to treat migraine and tension headaches; involuntary muscle contractions (dystonia) and spasms; and some localized pain conditions, including pain from shingles. Now one of the big Botox success stories is treatment of excessive sweating, or hyperhidrosis.
Botox injections are used for focal hyperhidrosis, in which the excessive sweating is limited to the armpits or palms and occasionally the soles of the feet. It's sometimes called idiopathic hyperhidrosis, meaning there's no known cause. Roughly 1%–3% of the population has the problem. About 30% of sufferers say that other family members are also affected, suggesting that there might be a genetic component to the condition.
Doctors and patients say that hyperhidrosis goes far beyond the occasional bouts of nervous perspiration we've all experienced. Sufferers change their shirts several times a day, wear colors that don't show sweat stains, and carry around paper towels to continually dab their palms. Bad cases can severely affect work and social life.
The body's "fight or flight" response — which
includes the sweat glands — is under the control of the sympathetic
nervous system. The sweat glands are activated by a chemical called
acetylcholine (pronounced a-see-til-CO-lean), and Botox works by keeping
nerves from releasing it.
The treatment for the armpits and palms involves 40–50 injections and takes less than half an hour. The needle is very fine, so they don't hurt very much. But injections into the palms often do hurt, and a local anesthetic is needed.
So far the best results have been for excessive sweating under the arms, which, in many cases, stops completely. With palms, the result is more often a reduction in sweating. The effect of the injections does wear off, so most people have to get them every 6–12 months. A study of about 200 axillary (armpit) hyperhidrosis patients in the June 2003 Archives of Dermatology found that the average time between injections was 7 months.
One lingering question has been whether repeat injections might become less effective. The study in the Archives found a slight drop-off, but good results over all. About 4% of patients developed compensatory sweating, but it was mild. Some patients who get injections for their palms notice slight muscle weakness, but it usually went away after several weeks.
September 2003 Update