Patch Testing with Disperse Blue Mix and Textile Dye Mix in Textile Dermatitis: Diagnostic Effectiveness, Co-Positivity and Clinical Relevance

Background/Objectives: Textile dermatitis seems underdiagnosed, partly due to low awareness of this problem and partly due to imperfect screening methods. The aim of this study was to analyse the diagnostic efficacy and clinical relevance of two textile dye mixes used in routine patch testing. Methods: Retrospective analysis of patch test results and clinical records of patients tested with textile dyes in a specialised patch test practice. Results: Between 2007 and 2024, 207 patients were patch tested with Disperse Blue Mix 106/124 (DBM). Positive reactions were observed in 17.4% of patients, including 10.6% considered clinically relevant. Between 2019 and 2023, 90 patients were tested with Textile Dye Mix (TDM) 6.6%, of whom 14.4% developed a positive reaction, relevant in 4.4%. In a subgroup tested with TDM 6.6%, DBM, all their components and cross-reacting azo dyes, out of eight patients with confirmed textile dermatitis, three cases would have been missed if screening had been performed using TDM alone (6.6%), compared with one case being missed if screening had been performed using DBM alone. The highest rate of positivity (78.6%) to TDM 6.6% was found among patients with an allergy to the common hair dye Toluene 2,5–Diamine Sulfate, all of whom were also positive to Disperse Orange 3 (DO3) present in TDM 6.6%. Among patients with positive tests to Disperse Blue (DB) 106 1% pet. or DB124 1% pet., 68.7% and 85.7%, respectively, reacted also to DBM 106/124 (each component at 0.5%), with respective figures for TDM 6.6% (DB106 and DB124 each at 0.3%) amounting to a mere 12.5% and 14.3%. Conclusions: The detection rates of textile dermatitis can be increased by improving screening tools for textile dye allergy in baseline series for routine patch testing. Based on the results of this study, proposed improvements include removing Disperse Orange 3 from the textile dye mix, tripling the concentrations of Disperse Blue 106 and Disperse Blue 124 in the textile dye mix, and doubling their concentrations in the Disperse Blue Mix 106/124.