The 2-Methoxymethyl Modification of p-Phenylenediamine Reduces the Sensitization Risk for Hairdressers to Hair Dyes—An Occupational Hand Exposure–Based Risk Assessment

Abstract

BackgroundAllergic contact dermatitis involving the hands is a common occupational skin disease for hairdressers and the potent sensitizers p-phenylenediamine (PPD) and toluene-2,5-diamine (PTD) are associated with the development of occupational allergic contact dermatitis.ObjectiveThe aim of the study was to analyze whether the use of the moderate sensitizer 2-methoxymethyl-PPD (ME-PPD) in professional hair dyes is a suitable tool to reduce the occupational contact allergy risk for hairdressers.MethodsHand exposure of hairdressers (N = 11) to ME-PPD was analyzed under routine hair coloring conditions in commercial salons. By accounting for wet work and uneven hand exposure, the daily hand exposure was derived and compared with the occupational acceptable exposure level (AEL), that is, the sensitization induction threshold of ME-PPD adjusted for interindividual variability among workers.ResultsThe daily hand exposure to ME-PPD was 1.6 μg/cm2, and the occupational AEL was 215 μg/cm2. The ratio of hand exposure to AEL was calculated as the margin of safety (MOS) against occupational sensitization. For ME-PPD, the MOS of 134 indicates a low likelihood of sensitization versus PPD and PTD with MOS values of 2.7 and 5.9, respectively.ConclusionsOur data predict that the use of ME-PPD in professional hair color products improves the protection of hairdressers against hair dye–related contact allergy versus the use of PPD and PTD.