Chemical investigations of disperse dyes in patch test preparations

Background:  Contact allergy to textile dyes is not uncommon. The allergy is detected by patch testing patients with commercial patch test preparations.
Objective:  To investigate 8 disperse dyes (DDs) used for patch testing in the departments in Malmö and in Leuven and to compare them with test preparations used at various dermatology departments.
Materials/Methods:  The investigated DDs were Disperse Blue (DB) 35, 106, and 124, Disperse Yellow (DY) 3, Disperse Orange (DO) 1 and 3, and Disperse Red (DR) 1 and 17. From 13 clinics, 107 petrolatum preparations were analysed using high-performance liquid chromatography and thin-layer chromatography (TLC), and compared with reference substances obtained at the Malmö laboratory. Concerning DB 35, no reference substance could be identified.
Results:  TLC visualized impurities in all DDs. For each DD, except DB 35, the mean concentration in the preparations labelled to contain 1.0% (w/w) were DB 106: 0.30%, DB 124: 0.25%, DY 3: 0.44%, DO 1: 0.40%, DO 3: 0.68%, DR 1: 0.49%, and DR 17: 0.35%; there were variations between the samples also with regard to the number of impurities. DO 3 could not be demonstrated in 4/15 preparations labelled DO 3.
Conclusion:  The results may have implications for individual diagnosis and prevention and when comparing test results from various centres.