Contact allergy to hair colouring products The cosmetovigilance experience of 4 companies (2003-2006)

The post-marketing undesirable events to hair colouring products in the European Union notified to the cosmetovigilance departments of four major cosmetic companies were analysed (2003-2006). The objective was to determine whether there was any time effect (trend to increase or decrease), country effect (significant difference between the countries included in the analysis) or product type effect (direct or oxidation), as well as to identify risk factors. Alleged undesirable events (UEvs, all notifications prior to causality assessment), were compared to the respective undesirable effects (UEfs, reasonably attributable to product use). A detailed analysis was performed on notifications with manifestations compatible with allergic contact dermatitis. No time effect of UEvs and UEfs was shown, for all hair-dye associated notifications and for allergic contact dermatitis, for all hair colouring products together and by product type. The incidence of allergic contact dermatitis to direct hair colouring products was lower for all four companies compared to oxidative hair dyes. The reporting rates of UEfs were statistically higher in the UK for one of four companies. Past history of black henna tattoos appeared as a major risk factor for seriousness of allergic contact reactions.