Background: In recent years, the alarming increase in contact allergy to hair dyes has drawn much attention. It has been shown that many of the currently allowed hair dye substances are potent skin sensitizers.
Objectives: To study the prevalence of hair dye substances, categorized as potent skin sensitizer, in oxidative hair dye products on the Swedish market.
Materials and methods: Ingredient labels of 122 oxidative hair dye products from 20 brands were examined. All ingredients were recorded, and the prevalence of hair dye substances categorized as potent skin sensitizers was assessed.
Results: According to ingredient labelling, 120 out of 122 examined oxidative hair dye products contained hair dye substances categorized as potent skin sensitizers. More than 80% of the products contained at least four such substances; 37 hair dye substances categorized as potent skin sensitizers were identified, and 10 of these were more prevalent than p-phenylenediamine.
Conclusions: Hair dye substances categorized as potent skin sensitizers are very common in oxidative hair dye products. A substantial number of potent skin sensitizers are more frequently used than p-phenylenediamine, while only a few are commercially available as patch test substances.