Pre-testing in hair dye users: an assessment of the Colourstart system.

To avoid adverse reactions to allergenic ingredients, manufacturers recommend "sensitivity testing" prior to use of hair dyes. However, there is no standardised method and the recommendation is often not followed. We assessed the ability of a standardised test system from one manufacturer (Colourstart, a small skin surface water-slide transfer containing p-phenylenediamine (PPD)) for its ability to elicit a reaction in those with a previously diagnosed contact allergy to PPD, the main hair dye allergen. Thirty volunteers with diagnosed PPD allergy (10 each of 3+, 2+ and 1+) were assessed with the Colourstart system according to the manufacturer's instructions. Responses were recorded after 48h exposure. Colourstart identified 100% of those with a 3+ reaction to the diagnostic patch test, 80% of the 2+ reactors and just 10% of the 1+ reactors. Thus, Colourstart successfully identified those individuals with the greatest sensitivity to PPD, who might therefore be at risk of a severe reaction if they dyed their hair. It also identified 83% of those who reported a severe/very severe history of hair dye adverse reaction. However, its proper use and interpretation are necessary if those consumers most at risk are to have the information necessary to avoid serious adverse reactions to hair dyes.