This study analyzes the suppression of sweat gland activity by botulinum toxin type B. We injected botulinum toxin type B (between 2 and 1000 mouse units subcutaneously) in the lateral side of both lower legs in 15 healthy volunteers. Sweat tests were carried out before botulinum toxin type B injections, and at 3 wk, 3 mo, and 6 mo. We studied focal anhidrosis by iodine-starch staining and by capacitance hygrometry after carbachol iontophoresis, according to the quantitative sudomotor axon reflex test (QSART). Iodine starch staining indicated that a threshold dose of 8 mouse units botulinum toxin type B leads to anhidrotic skin spots (>4 cm2) after 3 wk. Duration of anhidrosis was prolonged for 3 mo when 15 mouse units and for 6 mo when 125 mouse units botulinum toxin type B were injected. The size of the anhidrotic area decreased with time (p<0.001), indicating partial recovery at the edges. After 3 wk, the QSART score had significantly decreased to 18% of baseline and had decreased to zero in most subjects with doses of 62.5 mouse units or more. After 3 mo, the QSART had returned to 91% of baseline in all but one subject and, after 6 mo, recovery of sudomotor function was complete. Analysis by iodine-starch staining and QSART indicated that botulinum toxin type B suppresses sudomotor function effectively, in a concentration-dependent manner.

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