Local treatment - botulinum toxin
Botulinum toxin is a potent substance that affects the nervous system. It is produced by the bacterium Clostridium botulinum. It causes botulism - a severe and often fatal type of food poisoning.
The purified form of the toxin produced by strain A of the bacterium is commercially available for therapeutic use (BOTOX - Allergan; Dysport - Speywood).
The toxin is commonly used in the treatment of a number of muscular and nerve problems including twitching of the eyelid, torticollis and spasms in cerebral palsy. Loss of sweating was noted as a side effect of treatment for some of these conditions.
Botulinum toxin works by entering the end of a nerve and blocking the release of chemicals required to relay electrical signals to the tissue supplied by that nerve. This effect does not last forever and will wear off after a few weeks.
Various studies on the use of botulinum toxin for localised hyperhidrosis have been published. They all show that the introduction of the toxin into the skin significantly reduces sweating for 4-6 months following a single injection. The injections can be repeated once the effect has worn off. Subsequent courses of treatment may last longer.
To treat the armpit a number (approx. 20) injections have to be made into the skin on each side. This is well tolerated without any form of anaesthetic. Injections can also be made into the palm of the hand and the sole of the feet. This procedure is more painful and requires some form of anaesthesia. In the hand the small muscles may be affected causing mild weakness.
The risk of side-effects can be minimised by avoiding injections under the skin and administering small doses of the drug at many sites.