UV-B Irradiation Attenuates Dermal Effects of Botulinum Toxin A: A Randomized, Double-Blind, Placebo-Controlled Study THOMAS SYCHA, MD, Ã NICOLE KOTZAILIAS, MD, Ã GOTTFRIED KRANZ, MD, Ã FRANZ TRAUTINGER, MD, y PETER SCHNIDER, MD z AND EDUARD AUFF , MD Ã BACKGROUND Botulinum toxin type A (BoNT/A) is frequently used for cosmetic indications and hyperhidrosis. OBJECTIVES We investigated whether UV-B irradiation alleviates the BoNT/A effect on local sudomotor activity. MATERIALS AND METHODS In a randomized, double-blinded trial, the anhidrotic areas after BoNT/A (100 mU) injection 48 hours before and 14 days after UV-B irradiation were compared in six healthy volunteers. RESULTS UV-B irradiation alleviated BoNT/A effect by approximately 30% (p = .0017). The UV-B–evoked reduction of anhidrotic areas was constant over the observation period of 14 weeks. CONCLUSIONS When BoNT/A is applied intradermally, excessive exposure to UV-B and sunburn should be reconsidered. The authors have indicated no significant interest with commercial supporters. B otulinum toxin type A (BoNT/A) is a clostridial neurotoxin that inhibits acetylcholine release from peripheral cholinergic terminals and thereby blocks the neuromuscular and neuroglandular junction. The approved dermatologic indications for BoNT/A are glabellar rhytides 1,2 and focal hyperhidrosis. 3–5 The optimal treatment requires proper patient se- lection, 6,7 precise dosing, 1,2,8 and accurate injection techniques. 9,10 Furthermore, the protein structure of BoNT/A implies its instability, although this appears not to be as problematic as previously reported. Recent studies show that agitation while reconstitu- tion and the storage of solved toxin for extended periods do not affect BoNT/A’s potency. 10 Never- theless, exposure to ultraviolet radiation may be expected to alleviate BoNT/A effects after intrader- mal injection. In this study we explored whether UV-B exposure can attenuate the effect of intradermal BoNT/A. We thereby sought to clarify the importance of avoiding intensive sun exposure after intradermal BoNT/A treatment. Methods Subjects, Study Design, and Drug Administra- tion The study was approved by the local ethics com- mittee and the study protocol conformed to the guidelines of the 1975 Declaration of Helsinki. Six healthy volunteers (five male, one female, age 30–40 years) participated in the study after written in- formed consent and medical history were obtained. Subjects agreed to avoid additional UV exposure during the study period. The first part of the study was performed using a randomized, double-blind design. For each subject, two syringes were prepared, one containing 0.5 mL [ = 100 mouse units (MU)] of BoNT/A (Dysport, Ipsen, Wrexham, UK; reconstituted from 500 MU with & 2007 by the American Society for Dermatologic Surgery, Inc.  Published by Blackwell Publishing  ISSN: 1076-0512  Dermatol Surg 2007;33:S92–S96  DOI: 10.1111/j.1524-4725.2006.32338.x S92 Ã Department of Neurology and y Department of Dermatology, Medical University of Vienna, Vienna, Aus- tria; z Department of Neurology, Landeskrankenhaus, Grimmenstein-Hochegg, Austria