I have many patients in which the botox or other neurotoxin doesn't last as long in suppressing wrinkles on the face -- especially those patients who exercise a lot or are very expressive. I have a few patients who have reported a similar effect in underarm, palm/sole, or back sweating. These patients typically require higher doses to maintain another patients similar clinical effect. It appears to me that when there is more neurological activity, the toxin is challenged and new or alternate connections are made to compensate. This is not something that anyone should be concerned about, and is not something I hear often, but i thought it would be best to report. I wish you the best of luck, Dr. Emer.