Botulinum toxin is a treatment of choice for severe hyperhidrosis, according to Mr Jack Collin and Dr Paul Whatling (consultant surgeon and higher specialist trainee, John Radcliffe hospital, Oxford).
The excessive sweating of hyperhidrosis is caused by innervation of the eccrine sweat glands. The neurotransmitter involved is acetylcholine. Botulinum toxin binds to presynaptic nerve membranes and inhibits the release of acetylcholine.
In a review of hyperhidrosis treatment, Drs Collin and Whatling say that, in a small study of patients with disabling hyperhidrosis, botulinum toxin "completely abolished sweating in the injected areas after a delay in onset of two to three days. The effect lasts for up to 11 months". However, they caution that, while second and third treatments have been effective, in the long term antibody formation may reduce therapeutic potency.
Botulinum toxin is given by subdermal injection to the area of hyperhidrosis. The study involved doses of 240 units of botulinum A toxin given as 12 injections of 0.1ml in the armpit. For the feet, a larger dose was required. No adverse effects were observed in over 20 patients treated. The Oxford doctors comment that the risk of paresis of the hand muscles prevents its use in hyperhidrosis of the hand. In such patients, surgery is a safer alternative (British Medical Journal 2000;320:1221).