Prevalenza della sensibilizzazione da contatto ad alcuni coloranti permanenti per capelli

Background: permanent hair dyes are a common cause of allergic contact dermatitis (ACD) in hairdressers and their clients. The sale of these products has progressively decreased in recent years, despite their improved quality and safety. Objectives: the aims of this study were to determine a) the present prevalence of contact sensitivity to p-phenylenediamine (PPD), p-toluenediamine (PTD) and disperse orange 3 (DO3), b) the trend of concomitant or cross reactions to these three dyes, and c) the possible use of PTD and/or DO3 as an alternative to PPD. Materials and methods: 8,573 consecutive patients affected by eczematous dermatitis were patch tested with PTD sulphate, DO3, PPD free base (each 1% in pet.) and the other allergens of the SIDAPA standard series according to the GIRDCA guidelines. The results were statistically analysed. Results and conclusions: allergic reactions to one or more hair dyes were observed in 318 subjects (3.7%). PPD were positive in 307 (3.6%), DO3 in 121 (1.4%) and PTD in 86 (1.1%). Therefore, PPD is still an important contact sensitizer and the best indicator both of allergy to aromatic compounds with an amino group in the para-position and of ACD from hair dye related chemicals. Hair colouring preparations were the most frequent cause of PPD sensitization (199/318), followed by rubber articles (26/318) and textile dyes (19/318). Of the 199 subjects with ACD from hair dyes, 100 (50.3%) showed concomitant positive reactions to PPD, DO3 and/or PTD. Therefore, DO3 and PTD are not alternative to PPD.