Chemical investigations of disperse dyes in patch test preparations.

Contact allergy to textile dyes is not uncommon. The allergy is detected by patch testing patients with commercial patch test preparations. 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. 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. 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. The results may have implications for individual diagnosis and prevention and when comparing test results from various centres.