BOSTON (AP) - Injections of botulism toxin can control an embarrassing condition that makes people sweat so heavily that their clothes get drenched at room temperature, a German study has found.

The research adds to the growing list of diverse medical uses for the powerful food-borne poison, which is already used in diluted form to smooth out forehead wrinkles and ease migraine headaches.

"The effectiveness is really hard to believe," said dermatologist Dr. Richard Glogau of the University of California at San Francisco. Glogau said the findings help establish the toxin as the treatment of choice for hyperhidrosis, a sweating disorder.

Hyperhidrosis, whose cause is unknown, makes people sweat so profusely that they are often humiliated at school or work. Sweaty palms prevent them from shaking hands comfortably, gripping a tool securely or working normally at a keyboard.

"The people who suffer from it are enormously affected," said neurosurgeon Dr. Raj Narayan of Temple University in Philadelphia, who operates on some of these patients. "They also suffer from the fact that nobody else seems to think it's a particularly big deal."

The nerve-paralyzing botulism toxin is one of the most powerful poisons known to medicine and is feared as a potential biological weapon.

In the study published in Thursday's issue of The New England Journal of Medicine, doctors injected the diluted toxin into the armpits of 145 patients with hyperhidrosis.

At the start of the University of Munich study, patients were producing sweat at a rate of up to four cups over eight hours under both arms combined. Two weeks after the injections, they were sweating an average of only 15 percent of the initial rate. The toxin reduced sweat to normal levels in virtually all patients.

It works by blocking the release of a chemical needed to transmit nerve signals to muscles and sweat glands.

The effect is temporary. Patients slowly began sweating more heavily after two weeks. But even after 26 weeks, they were perspiring on average less than half of their beginning rate. Injections must be repeated every three to six months. The same treatment can be applied to the hands.

Overall, the botulism injections appear to be more effective than other treatments, doctors said. In one technique, the hands are placed in water and exposed to a weak electrical current. The direct application of aluminum chloride, used in deodorants, also helps to dry armpits. As a last resort, surgeons cut or crimp nerves that activate the sweat glands.

However, the toxin is expensive, with a typical treatment costing $ 1,000 to $ 1,500 in the United States. Insurance companies generally will not cover the cost. There are also questions about whether repeated treatments can cause nerve damage and over the frequency of allergic reactions.

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