Two decades of p-phenylenediamine and toluene-2,5-diamine patch testing - focus on co-sensitizations in the European baseline series and cross-reactions with chemically related substances.

BACKGROUND: Cross-reactions and co-sensitizations are of great importance in understanding contact allergy and exposure sources. OBJECTIVES: To investigate common cross-reactions and co-sensitizations in p-phenylenediamine (PPD)-sensitized and toluene-2,5-diamine (TDA)-sensitized individuals. METHODS: From our patch test population, 8036 patients patch tested with the European baseline series were extracted. Readings had to be performed at least on day 3 according to ICDRG guidelines. RESULTS: Two hundred and fifty-one patients were sensitized to PPD and/or TDA; 231 patients were sensitized to PPD, and 109 to TDA. Significant differences were observed regarding the strengths of patch test reactions to PPD and number of cross-reactions. For TDA, a difference was found between all reaction strengths, except between + and ++ strengths. PPD-sensitized individuals were more likely to be sensitized to carba mix, cobalt chloride, colophonium, p-tert-butyl phenolformaldehyde resin, paraben mix, and methylisothiazolinone. TDA-sensitized individuals were more often sensitized to carba mix. CONCLUSIONS: Cross-reactivity was commonly found among individuals sensitized to PPD or TDA, and was strongly related to the strength of the patch test reaction. Regarding co-sensitizations, a frequently appearing or common exposure source could not be determined. However, modification of the allergen by, for example, the skin microbiota may have caused the formation of molecules that are, for the human immune system, indistinguishable from PPD.

ESSCA results with the baseline series, 2002-2012: p-phenylenediamine.

BACKGROUND: Allergic contact dermatitis caused by p-phenylenediamine (PPD) is common among all age groups and both sexes. Monitoring of prevalence and intensity of sensitization is important. OBJECTIVE: To evaluate contact allergy to PPD in Europe, and to compare reaction intensities in different European regions. METHODS: Data collected by the European Surveillance System on Contact Allergies (ESSCA) network between 2002 and 2012 from 12 European countries were analysed regarding prevalence, grading of positive reactions to PPD, and relevance. RESULTS: A total of 99 926 PPD-positive patients from 63 departments were included for analysis. The overall (2002-2012) prevalence of PPD sensitization in Europe is ∼4%. Stratified for country, the highest overall standardized prevalence was found in Lithuania, and the lowest in Slovenia. The prevalence of PPD sensitization did not decline over the years. In the southern European countries, higher numbers of strong and extremely strong reactions were registered. The clinical relevance of PPD sensitization varied from half to three-quarters. CONCLUSION: The prevalence of PPD sensitization has not changed over time. Strong and extremely strong patch test reactions are seen more often in the South, probably because of the higher number of PPD-containing hair dye products.

The role of the antioxidant ascorbic acid in the elicitation of contact allergic reactions to p-phenylenediamine.

BACKGROUND: An allergic contact reaction is accompanied by high oxidative stress in the skin. Pretreatment of the skin with antioxidative substances could reduce the elicitation reaction. OBJECTIVES: To investigate, in a proof-of-principle study, whether pretreatment of the skin with the antioxidant ascorbic acid reduces the elicitation reaction to a p-phenylenediamine (PPD)-containing hair dye in sensitized subjects. METHODS: Twelve subjects with contact allergy to PPD, a documented skin reaction to a hair dye simulation exposure model and a history of hair dye-related skin complaints were included in this study. Skin areas on the forearms were, in a left versus right design, exposed to an emulsion with ascorbic acid and an emulsion without ascorbic acid, and then to a 2% PPD-containing hair dye testing formulation. In addition, control areas were exposed to the emulsions and to the PPD-containing hair dye formulation without pretreatment. Skin reactions were graded on day (D)2 and D3. RESULTS: Pretreatment with ascorbic acid emulsion resulted in a reduction in the elicitation reaction in 7 of 12 subjects at D3 (p = 0.046). No statistically significant difference was observed at D2. CONCLUSIONS: Pretreatment of the skin with the antioxidant ascorbic acid had an attenuating effect on the elicitation reaction to PPD in sensitized individuals.

p-Phenylenediamine exposure in real life - a case-control study on sensitization rate, mode and elicitation reactions in the northern Netherlands.

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.