Fragrance mix I patch test reactions in 5006 consecutive dermatitis patients tested simultaneously with TRUE Test® and Trolab® test material

Background: The prevalence of contact allergy to fragrance mix (FM) I varies from study to study, depending on factors such as test population, patch test material, and technique. Objectives: To compare the outcome of routine patch testing with FM I TRUE Test and FM I Trolab. Materials and Methods: A total of 5006 consecutive eczema patients were patch tested with both patch test materials according to the International Contact Dermatitis Research Group. Results: A total of 9.9% patients tested had a positive reaction to one of the FM I mixes; 4.4% to FM I TRUE Test, 9.3% to FM I Trolab, and 3.7% to both (P < 0.0001). Patients with a stronger reaction to FM I TRUE Test almost all reacted to FM I Trolab, whereas the reverse situation showed a lower association. Clinical relevance of a positive patch test reaction to FM I TRUE Test was found in 73.0%, and clinical relevance of a positive patch test reaction to FM I Trolab was found in 64.3%; 68.4% of the patients with a positive reaction to FM I TRUE Test and 54.3% with a positive reaction to FM I Trolab were positive to one or more of the eight constituents of the mix. Limitations: The study is retrospective, and supplementary testing with FM components in patients with a positive reaction to the mixes was performed in a selected group of patients. Determination of clinical relevance may be biased. Conclusions: From this study, we cannot conclude which of the two FM I test preparations is the best for diagnostic purposes. Inclusion of both FM I tests in the baseline series to obtain a graded degree of FM I allergy for the individual patient is one option. Prospective controlled patch test studies with FM I patch test material are recommended.