RESUMO
BACKGROUND: The prevalence of p-phenylenediamine (PPD) sensitization is 4% in the patch tested population and varies between zero and 1.5% in the general population. Hair dye is a recognised sensitization source. OBJECTIVES: To define the prevalence rates of PPD sensitization in the general and patch tested populations of The Netherlands, and to gain insights into relationships between patch test strength and exposure sources. METHODS: Patch test database cases were matched with population-based controls. Analyses were performed based on demographic details, patch test reactions, and potential PPD exposure. RESULTS: PPD sensitization occurred in 3.3% of the patch tested population and in 1.3% of the general population. Hairdressers had a 4.4-fold increased chance of being sensitized to PPD (p = 0.041), and black henna tattoos showed a tendency for a 2.3-fold increased chance of sensitization (p = 0.081). Weak elicitation reactions were present in hairdressers and consumers. However, cases who had had black henna tattoos showed significantly more (extremely) strong patch test reactions upon elicitation (p = 0.015). CONCLUSIONS: The prevalence rates in the patch tested and general population of The Netherlands are comparable with the prevalence rates of other mid-European centres. PPD sensitization is often attributed to hair dye. However, this study shows that subjects sensitized by black henna tattoos present with very severe elicitation reactions, emphasizing the need for more strict policing the prohibition.