Influence of vitamin C on the elicitation of allergic contact dermatitis to p-phenylenediamine

Background. Hair dyes represent one of the most important causes of allergic contact dermatitis resulting from the use of cosmetic products. The principal causative chemistry is associated with oxidation products of p-phenylenediamine (PPD) and closely related substances. Objectives. To examine whether prior application of the antioxidant vitamin C to the skin was able to reduce the cutaneous allergic response to PPD. Methods. Twenty eight volunteers with a proven history of contact allergy to PPD were recruited. Each was tested with a range of PPD doses and PPD-containing hair dye on untreated skin and skin pretreated for 10 min with a vitamin C formulation. Results. Pretreatment of skin sites with vitamin C led to a reduction in the intensity, or even ablation, of the cutaneous allergic reaction to PPD in similar to 75% of cases as compared with untreated skin. Conclusions. The results suggest that treatment of the skin adjacent to the hair-bearing area with antioxidant could form part of a strategy to reduce the burden of cosmetic allergic contact dermatitis caused by hair dyeing.