Hyperhidrosis is a condition characterized by over-secretion of sweat, most commonly in the underarms and the palms. It can take a heavy toll on those affected, leading to embarrassing social situations and limitation on career mobility. Underarm hyperhidrosis, besides causing wet clothing, can cause skin maceration, skin infections, and unpleasant body odors.
Sweating in hyperhidrosis can arise from different triggers. Localized underarm and palmar hyperhidrosis is usually triggered by emotional stimuli. Generalized hyperhidrosis, with overactive sweating of much of the body, may be associated with certain medical conditions, such as diabetes, hyperthyroidism, and cancer. Therefore, when seeking treatment for excessive sweating, it is important to exclude medical causes of the disorder.
Treatment of hyperhidrosis is varied. Only recently has a low-impact, yet effective treatment become available, in the form of botulinum toxin (Botox). Local treatments for hyperhidrosis include metal salts, such as aluminum chloride. These salts function by plugging up the ducts of the seat glands. This needs to be performed daily at the commencement of treatment, then followed with maintenance regimen once or twice a week. Another method is tap water iontophoresis. The hands or feet are immersed in tap water for 10 minutes while an electric current is applied. The mechanism of action is unknown. Treatments are usually performed several times a week. Surgical treatment is also an option. The sympathetic nerves in the chest can be cut. Finally, the sweat gland-bearing underarm skin can be surgically removed.
Botulinum toxin A (Botox) is a chemical produced by a bacteria, clostridium botulinum. It is the substance found to be responsible for botulism. Botulinum toxin was first used therapeutically in the 1960’s by ophthalmologists, for the treatment of eye muscle disorders. Use of botulinum toxin spread with the treatment of other disorders of muscle spasm. Finally, it was applied cosmetically for the treatment of dynamic facial wrinkles. Simultaneously, it was noted that patients had decreased sweating in areas where botulinum toxin was injected. This led to investigation into its use for hyperhidrosis.
Sweat glands secrete sweat in response to the release of a neurotransmitter, acetylcholine, from nerve endings. Botulinum toxin functions by blocking the release of acetylcholine from the nerve endings. It is not known hoever, whether this is the definitive mechanism of action of botulinum toxin in hyperhidrosis treatment.
Botulinum toxin A, is commercially available as BOTOX in the United States. It is used clinically as follows. Prior to injection, the area of sweating is visualized using the Minor test. First, iodine is applied to the skin and allowed to dry. Corn starch is applied and turns blue in areas where sweating is occurring. The loose starch is then brushed off, allowing one to see where injection is needed. In the underarms, a standard dose of 50 units per side is generally needed and is broken up into smaller aliquots that are injected throughout the involved area. Injection in the underarms is well tolerated and doesn’t require anesthetic. Treatment of the palms and soles, however, is very painful and requires nerve block in the wrist or ankle or the use of topical anesthetic cream.
BOTOX takes effect after approximately 3 days, and is usually maximal after one week. It is approximately 90% effective and generally lasts about 7 months, with a range of 3 to 17 months. In a study by Hornberger et al, mean sweat production at 24 weeks was still below 50% of the preinjection level. 92% of patients were satisfied with the treatment at 4 weeks after injection. Higher doses can somewhat prolong the duration of effect, but at an unacceptably increased cost. Repeat treatments do not lead to the decreased need for BOTOX in the future.
Side effects include those that would be expected from poking the skin with a needle, such as bleeding or infection, although these are uncommon. Rarely, repeated use of botulinum toxin can lead to the development of antibodies to it. This is not harmful but causes the toxin to become ineffective. Use of the toxin in the palm can lead to temporary weakness of hand muscles. Pregnancy, breast feeding, and certain conditions of muscle dysfunction, such as Myasthenia Gravis, are contraindications to the use of botulinum toxin.
In conclusion, when hyperhidrosis causes extreme discomfort or anxiety for an individual, botulinum toxin is the ideal treatment, despite the expense and the need for repeat treatments.