Myroxylon pereirae (Balsam of Peru): still worth testing?

BACKGROUND Based on the facts that Myroxylon pereirae (MP), or Balsam of Peru, is nowadays almost not used "as such", and fragrance mix 1 (FM1) apparently is more sensitive in detecting fragrance allergy, the usefulness of testing MP in baseline series was recently questioned. OBJECTIVES Identification of the number of clinically relevant patch test reactions to MP not detected by FM1. METHODS Retrospective analysis of 12 030 patients patch tested with MP and FM1 for contact dermatitis between January 2018 and December 2019 in 13 Italian dermatology clinics. RESULTS 439 patients (3.6%) had positive patch test reaction to MP, 437 (3.6%) to FM1. Positive reactions to MP and FM1 were observed in 119 subjects (1.0%), 310 (2.6%) reacted to MP only, 304 (2.5%) to FM1 only, 5 to MP and sorbitan sesquioleate (SSO), 9 to FM1 and SSO, 5 to MP, FM1 and SSO. Single sensitizations were clinically relevant in 75.2% of cases for MP (62.9% current, 12.3% past) and 76.3% for FM1 (70.1% current, 6.2% past). CONCLUSIONS Based on our results, MP appears still worth testing along with FM1 in baseline series, because it allows detection of a remarkable number of fragrance allergies, often relevant, which would be otherwise missed. This article is protected by copyright. All rights reserved.