University of Groningen. The dark side of p-phenylenediamine Vogel, Tatiana Alexandra

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1 University of Groningen The dark side of p-phenylenediamine Vogel, Tatiana Alexandra IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2016 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Vogel, T. A. (2016). The dark side of p-phenylenediamine: Biological aspects and prevalence of contact allergy to an extraordinary molecule [Groningen]: Rijksuniversiteit Groningen Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date:

2 Chapter 3 ESSCA results with the baseline series, : p-phenylenediamine Marie-Louise A. Schuttelaar1, Tatiana A.Vogel1, Francesca Rui2, Beata Krecicz3, Dorota Chomiczewska-Skora4, Marta Kieć-Świerczyńska4, Wolfgang Uter5, Francesca Larese Filon2 Dermatology, University Medical Center Groningen, University of Groningen, 9700 RB Groningen, The Netherlands 2 Department of Public Health, Occupational Medicine, University of Trieste, IT Trieste, Italy 3 Faculty of Health Science, Jan Kochanowski University, PL Kielce, Poland 4 Department of Dermatology, Nofer Institute of Occupational Medicine, PL Lodz, Poland 5 Department of Medical Informatics, Biometry and Epidemiology, University of Erlangen/Nürnberg, Erlangen, Germany 1 Submitted

3 Abstract Background: Allergic contact dermatitis to p-phenylenediamine (PPD) is common among all age groups and both genders. Monitoring of prevalence and intensity of sensitization is important. Objective: To evaluate contact allergy to PPD in Europe and to compare reaction strengths 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 analyzed regarding prevalence, grading of positive reactions to PPD, and relevance. Results: A total of PPD-positive patients from 63 departments were included for analysis. The overall ( ) prevalence of PPD sensitization in Europe is about 4%. Stratified for country the highest overall standardized prevalence was found in Lithuania, the lowest in Slovenia. The prevalence of PPD sensitization did not decline over the years. In the Southern European countries a higher number of strong and extremely strong reactions were registered. The clinical relevance of PPD sensitizations varied from half to three quarters. Conclusion: The prevalence of PPD sensitizations has not been changed over time. Strong and extremely strong patch test reactions are observed more often in the South, probably due to the higher number of PPD containing hair dye products. 42

4 3. ESSCA results with the baseline series, : p-phenylenediamine Introduction The aromatic amine p-phenylenediamine (PPD, 1,4-diaminobenzene, CAS no ) is a chemical that acts as an intermediate in dyes and antioxidants. PPD is the most important ingredient of oxidative (permanent) hair dye products. Its extreme protein binding capacity and its low molecular weight enable PPD to easily penetrate the hair shaft, but make it also a potent sensitizer, able to cause severe contact allergic reactions. 1 Most cases of contact allergy to PPD occur from contact with hair dye products in consumers and hairdressers. For several decades PPD has been tested in the European Baseline series. The prevalence of contact allergy to PPD in consecutive eczema patients varies widely between the different countries in Europe. 2 Thyssen et al. reported a weighted prevalence average of 4% in Europe. 3 The objective of this study was to evaluate contact allergy to PPD in patients with suspected allergic contact dermatitis (ACD), who were patch tested at centers of the ESSCA (European Surveillance System on Contact Allergies) network in the period from 2002 to Furthermore, in this study we compared the frequency of contact allergy to PPD and the reaction strength during patch testing between three different regions of Europe; the North, the Middle and the South. Methods Analyses in the present study are based on data included in the database of the network of European Surveillance System on Contact Allergies (ESSCA, This network has previously been described. 2 Patch test results have been obtained with the European Baseline Series, with possible national or departmental adaptations. These results were included in the database along with clinical and demographic data. The detailed characteristics of patients of the most recent period of analysis ( ) have been published. 4 The present paper addresses the frequency and time course ( ) of sensitization to PPD in consecutive patients, who were patch tested in 12 European countries. These European countries include Austria (AT), Switzerland (CH), Germany (DE), Denmark (DK), Spain (ES), Finland (FI), Italy (IT), Lithuania (LT), The Netherlands (NL), Poland (PL), Slovenia (SI) and the United Kingdom (UK). The countries are classified into three geographical regions to identify regional differences. These regions were defined as follows: North : Finland, Denmark, and Lithuania; Middle : Poland, Germany, Austria, Switzerland, The Netherlands, and United Kingdom; South : Spain, Italy and Slovenia. All patients included in the present analysis were patch tested with either PPD 1% pet. in investigator-loaded systems or in the TRUE Test (at a concentration of mg/cm 2. The vast majority of patch tests was investigator-loaded, while of the consecutive patients were patch tested with the TRUE Test, in altogether 5 departments. Most of these 43

5 patients were tested with the TRUE Test in The University Medical Center Groningen (NL; n=3987), followed by Hospital Universitario de La Princesa Madrid (ES; n=718), Department of Dermatology at León hospital (ES; n=242) and Amsterdam Free University Medical Centre (NL; n=180)) and a few patients in the Murcia department (ES; n=18). The patch testing procedure was conducted following international recommendations and readings were performed according to the ICDRG criteria. 5 At least one reading has been performed between D3 and D5 (inclusive) after application of the patch test. Weak (+), strong (++) and extremely strong (+++) positive patch test reactions were considered to be positive. From 2007 onwards, aggregated data had been exported from Copenhagen/Gentofte (DK). The Slovenian departments contributed information on reactions being positive or nonpositive. Hence, the distribution of reaction grades cannot be examined for these data. Relevance was based on patient interviews and was assessed by the physicians consulted. A clinically relevant patch test reaction was defined as follows: positive patch test (+/++/+++ reactions) to PPD in a subject with a current or a past dermatitis reaction, certain or probably caused or aggravated by exposure to a source of PPD. Analysis of clinical relevance of positive reactions was restricted to (i) departments patch testing with PPD and (ii) documenting relevance. The proportion of relevant reactions was based on non-missing data, i.e. missing data were considered to be completely missing at random. In other words, the patients with information were considered to be representative for all patients. All individuals with PPD contact allergy in whom the occupational code 5141 (ISCO-88) was documented were identified. Although this code also includes beauticians, experience indicates that >90% of these individuals are hairdressers. The proportion of relevance restricted to this group of hairdressers and the proportion of occupationally relevant positive PPD reactions were analyzed separately. Data management and analysis was performed using the statistical software R (version 3.1.3, In particular, besides crude prevalence rates of PPD contact allergy stratified for country and age, age and sex-standardized prevalence rates with accompanying 95% confidence intervals (CI) were also calculated. This allows the analysis of a comparison which is unconfounded concerning these two variables. Results The prevalence of PPD sensitization in the European countries A total of consultations involved patch testing with the European baseline series with PPD 1% petrolatum or in the context of the TRUE Test. Due to re-consultation of some patients, of whom the most current consultation was chosen, a total of patients were included for further analysis. Overall, the United Kingdom had tested the largest number of individuals each year. Spain, The Netherlands and Poland show an increase in the number of 44

6 3. ESSCA results with the baseline series, : p-phenylenediamine patients that were patch tested with PPD, from respectively 2009, 2009 and 2011 onwards. In Austria PPD has not been tested anymore since 2008, in Germany since Except for certain departments, which makes interpretation of German data difficult. The prevalence of sensitization to PPD stratified for the 12 European countries is shown in table S1 in the online supplement. Differences in prevalence of sensitizations were marked by year. Overall, the prevalence of PPD sensitizations varies around 4% and seems to be stable over the included years. There was no remarkable difference between crude and age- and sex-standardized prevalence rates. The highest prevalence of 9.3% in consecutive patients was seen in Lithuania in 2006, which had joined ESSCA only in Also in later years the prevalence in the Lithuanian department is relatively high. The lowest prevalence rates were found in Italy in 2002 (0.7%), albeit in quite limited data (n=185 tested), followed by Denmark in 2003 (1.5%). Table 1 provides data on the overall ( combined) prevalence rates of PPD sensitizations stratified for country. From all included countries Lithuania showed the highest overall standardized prevalence of PPD sensitizations, being 5.8%, followed by Austria (5.3%). The lowest prevalence rates were found in Slovenia (2.3%) and Denmark (2.5%). In general, more women than man have been patch tested. About three quarters of all PPD positive reactions were seen in women, varying from 65% in Germany to almost 87% in Slovenia. The highest prevalence amongst women was observed in Austria (6.1%) and amongst men in Lithuania (7%). The lowest prevalence rates were seen in Denmark and Slovenia, respectively. Only in Lithuania the prevalence of PPD sensitizations amongst men was higher than in women, although not significantly, considering the overlapping 95% CIs. The patch test strengths of all patients that were positively tested for PPD marked by country are also shown in Table 1. Strong and extremely strong patch test reactions are combined as one group. In general, in most of the countries more strong/extremely strong positive reactions than weak positive reactions were observed. Only in Austria, Germany, Lithuania and the Netherlands, more weak positive than strong/extreme positive reactions were seen. 45

7 Table 1: Results with PPD (1% pet. or included in the TRUE Test ) obtained in the ESSCA network , stratified for country. Males Females Overall Standardised Country n(test) + n (%) ++/+++ n (%)? /IR n (%) pos. n (%) pos. n (%) pos. n (%) pos. (%) (95% CI) (95% CI) (95% CI) (95% CI) AT (3.1) 37 (2) 0 (0) 17 (3.1) 76 (6.1) 93 (5.1) 5.3 ( ) ( ) ( ) ( ) CH (1.8) 123 (2.5) 147 (3) 55 (2.9) 158 (5.2) 213 (4.3) 4.4 ( ) (4.4-6) ( ) (3.8-5) DE (2) 99 (1.8) 65 (1.2) 72 (3.4) 138 (4.1) 210 (3.8) 3.8 ( ) ( ) ( ) ( ) DK 6315 (0.9) (1.2) (3.6) 46 (2.2) 109 (2.6) 155 (2.5) 2.5 (1.6-3) ( ) ( ) ( ) ES (0.5) 213 (3.8) 2 (0) 57 (3.2) 182 (4.8) 239 (4.3) 4.0 ( ) ( ) ( ) ( ) FI (1.3) 75 (2.6) 43 (1.5) 29 (2.8) 85 (4.6) 114 (3.9) 3.9 (1.9-4) ( ) ( ) ( ) IT (1.1) 432 (2.2) 71 (0.4) 136 (2) 517 (4.1) 653 (3.4) 3.4 ( ) ( ) ( ) ( ) LT (3.5) 37 (2) 9 (0.5) 28 (7) 73 (5.1) 101 (5.5) 5.8 ( ) (4-6.4) ( ) (4.6-7) NL (2.1) 129 (1.5) 61 (0.7) 79 (2.6) 233 (4.2) 312 (3.6) 3.6 (2-3.2) ( ) (3.2-4) (3.2-4) PL (1.2) 160 (3.5) 8 (0.2) 49 (3.6) 166 (5.1) 215 (4.7) 4.6 ( ) (4.4-6) ( ) (4-5.3) SI 5224 N.A. 122 (2.3) N.A. 16 (1) 106 (2.9) 122 (2.3) 2.3 ( ) ( ) ( ) ( ) UK (1.6) 788 (2.4) 108 (0.3) 267 (2.5) 1062 (4.8) 1329 (4) 3.9 ( ) (4.5-5) ( ) ( ) From 2007 onwards, aggregated data had been exported from Copenhagen/Gentofte (DK). For analyses addressing the distribution of + versus ++ and +++ reactions, the proportions from have been extrapolated and absolute numbers not given. The Slovenian departments contributed information on reactions being positive or non-positive, which was arbitrarily denoted as ++; hence, the prevalence of weak (as well as irritant) reactions cannot be interpreted, N.A.: not applicable. In Table 2 the number of individuals with a positive patch test reaction per country, combined with the percentage of clinical relevant reactions is shown. From the 63 departments participating in the ESSCA network, a total of 49 departments routinely documented clinical relevance. This indicates that 50 to 75 percent of all PPD positive patch test reactions have been considered clinically relevant. The number of PPD sensitized hairdressers as well as the percentage of relevant PPD sensitizations among hairdressers are shown, the latter being between 66 and 100 percent. Overall, however, occupationally relevant reactions are uncommon, varying from 0.5 to nearly 20 percent (in the United Kingdom and Poland, respectively). 46

8 3. ESSCA results with the baseline series, : p-phenylenediamine Table 2: Relevance of positive reactions to PPD (1% pet. or included in the TRUE-test ) in the ESSCA network , stratified for country. Country n (positive) % (relevant) n (hairdressers positive) % (hairdressers relevant) % (occupational relevant) AT CH DE ES FI IT LT NL PL UK Current and past relevance, certain or probable or not qualified regarding certainty has been aggregated. Denmark and Slowenia are excluded, as relevance information was not available (for a large part of the data). Analysis of relevance of positive reactions was restricted to (i) departments testing with PPD and (ii) departments documenting relevance at all (n=49). The first (leftmost) and third results column demonstrate the number of positive reactions overall and the number of hairdressers with positive reactions to PPD. % (relevant) : overall, i.e., irrespective of current and occupation; % (hairdressers relevant) : proportion of relevance restricted to hairdressers; % (occupational relevant) : the proportion of occupationally relevant positive PPD reactions irrespective of a certain occupation or the presence of occupational dermatitis. Differences in the prevalence and patch test strength of PPD sensitization between the European regions Figure 1 shows the annual age- and sex-standardized prevalence rates of sensitization to PPD stratified for three geographical European regions, and overall. Both the middle and the southern region did not show a great variety in the prevalence, as the mean prevalence was just below four percent. The northern region, however, demonstrated remarkable differences regarding the mean year prevalence, with significantly lower prevalence rates in 2002, 2003 and 2009 compared to the overall mean prevalence, mainly introduced by including Lithuania. 47

9 Figure 1: Age- and sex-standardised annual prevalences in the three regions (North, Middle, South) contributing to the ESSCA network and overall, with accompanying 95% confidence intervals. The grey figure within North is Denmark, the black figure is North including Denmark in the years that it contributed. The grey dotted line indicates the overall mean (3.9% positives). The distribution of the strength of the positive patch test reactions was compared between the three geographical regions in Europe. The results are shown in Figure 2, in which strong positive (++) and extremely positive (+++) reactions are combined. Differences were highly significant both in terms of overall heterogeneity and trend (p< in both cases, X 2 test), driven by the South region (there was no statistically significant difference between North and Middle ; p=0.45, X 2 test). Slovenia has been excluded in this analysis, as only a dichotomous outcome had been available. 48

10 3. ESSCA results with the baseline series, : p-phenylenediamine Figure 2: Proportion of + (light grey) and ++ or +++ (dark grey) reactions among all positive reactions as percent in three regions, North comprising Denmark, Finland and Lithuania, South Spain and Italy, and Middle the remainder (Slovenia has been excluded in this analysis as a dichotomous outcome had just been available). Total number of positive reactions given at the top. 49

11 Online Supplementary Table S1: Results with PPD (1% pet. or included in the TRUE-test ) obtained in the ESSCA network , stratified for country. Country AT 1 4.2% (16/378) 2.4% (8/332) 7.4% (25/339) 4% (12/297) 7.5% (26/346) 5.2% (6/115) N.T. N.T. N.T. N.T. N.T % ( %) 2.6% ( %) 7.8% ( %) 4% ( %) 7.5% ( %) 3.9% ( %) N.T. N.T. N.T. N.T. N.T. CH 1 2.5% (6/243) 4.8% (42/872) 4.8% (42/866) 3.2% (12/380) 5.2% (47/906) 4.2% (39/921) 3.2% (25/781) 2 2.8% (0.5-5%) 4.9% ( %) 4.8% ( %) 4.4% ( %) 5% ( %) 4.1% ( %) 3.4% (2-4.9%) DE 1 5% (72/1431) 3.5% (48/1367) 3.9% (49/1248) N.T. N.T. N.T. N.T. N.T. N.T. N.T. N.T % ( %) 3.5% ( %) 3.9% (2.7-5%) N.T. N.T. N.T. N.T. N.T. N.T. N.T. N.T. DK 1 1.9% (17/903) 1.4% (11/795) 3.2% (25/772) 2.8% (19/671) 3.2% (20/632) 1.7% (13/749) 3.4% (28/830) 2.3% (22/963) 2 1.7% ( %) 1.5% ( %) 2.9% ( %) 3% ( %) 3.5% (1.9-5%) 1.7% ( %) 3.3% (2-4.6%) 2.4% ( % ) ES 1 8.2% (28/340) 7.5% (28/371) 5.4% (10/185) 4.2% (17/400) 5.9% (7/118) 3% (36/1213) 3.3% (34/1029) 3.6% (40/1098) 4.7% (39/828) 2 7.9% ( %) 6.8% ( %) 4.4% ( %) 3% ( %) 4.1% (1.2-7%) 2.6% ( %) 3.2% ( %) 3.5% ( %) 5.1% ( %) FI 1 3.2% (9/281) 2% (7/345) 2.5% (6/237) 4.6% (11/240) 5.4% (20/369) 4.9% (19/391) 2.3% (7/302) 3.3% (10/303) 5.4% (17/313) 6.1% (8/132) 2 2.7% ( %) 2.2% ( %) 2.2% (0.4-4%) 4.4% ( %) 5.3% (3-7.7%) 4.7% ( %) 2.6% ( %) 3.3% ( %) 5.8% ( %) 6.9% ( %) IT 1 1.6% (3/185) 2.9% (44/1499) 3.8% (93/2468) 2.5% (39/1568) 3.1% (32/1021) 3.3% (58/1737) 3.3% (58/1759) 3.2% (62/1951) 3.6% (98/2693) 3.8% (98/2586) 3.4% (68/2016) 2 0.7% (0-1.6%) 3.2% ( %) 3.9% ( %) 2.7% ( %) 3.3% ( %) 3.3% ( %) 3.5% ( %) 3.2% (2.4-4%) 3.7% ( %) 3.7% (3-4.4%) 3.3% ( %) LT 1 9.5% (4/42) 7.4% (2/27) 7.4% (16/215) 3.9% (13/337) 6.5% (22/337) 4.6% (17/370) 5.5% (27/495) 2 8.2% ( %) 5.7% (0-13.5%) 9.3% ( %) 4.2% ( %) 6.3% ( %) 4.6% ( %) 5.8% ( %) NL 1 2.5% (10/393) 4.8% (17/353) 3.3% (22/671) 3.2% (34/1058) 3.8% (41/1080) 3.2% (12/378) 3.4% (13/387) 4% (32/796) 3.7% (41/1096) 3.6% (43/1189) 3.9% (47/1203) 2 2.7% (1-4.5%) 5.4% ( %) 3.5% (2-4.9%) 3.2% ( %) 3.7% ( %) 3.1% ( %) 3.4% ( %) 4% ( %) 3.6% ( %) 3.5% ( %) 3.8% ( %) PL 1 N.T. 4.7% (13/275) 5.3% (19/360) 4.3% (13/303) 4.9% (15/307) 6.2% (18/292) 3.7% (11/296) 4.6% (24/521) 4.4% (23/528) 5.9% (54/909) 3.1% (25/797) 2 N.T. 4.1% ( %) 6% ( %) 4.3% (2-6.6%) 4.8% ( %) 6.1% (3.3-9%) 3.6% ( %) 4.6% ( %) 4.3% ( %) 5.9% ( %) 2.8% (1.7-4%) SI 1 2.4% (21/869) 1.3% (13/1001) 2.6% (32/1245) 2.7% (56/2109) 2 2.3% ( %) 1.3% ( %) 2.7% ( %) 2.7% (2-3.4%) UK 1 2% (7/342) 3.5% (18/511) 4% (126/3173) 4% (97/2434) 3.9% (126/3233) 4.4% (144/3250) 3.8% (186/4854) 3.6% (194/5333) 4.1% (182/4412) 4.5% (128/2819) 4.4% (121/2766) 2 1.7% (0.4-3%) 3.4% ( %) 4.1% ( %) 3.9% ( %) 3.9% ( %) 4.3% ( %) 3.8% ( %) 3.5% (3-3.9%) 4% ( %) 4.4% ( %) 4.1% ( %) 1: Crude percent positive (number of positive reactions/ number of patients tested). 2: Age and sex-standardised percent positive (95% confidence interval (CI)). 50

12 3. ESSCA results with the baseline series, : p-phenylenediamine Discussion No remarkable decreases in the prevalence of PPD sensitizations This study showed the development of sensitization to PPD from 2002 to 2012, in 12 European countries and stratified in three geographical regions. The overall prevalence of about 4% was stable during the study period. Furthermore, no decrease of PPD sensitization was observed within the patch tested population stratified by country, although the maximum permitted concentration of PPD in consumer products has been limited to 2% in the final product in 2009 (amending Annex III to Regulation (EC) No 1223/2009 of the European Parliament and of the Council on cosmetic products). The Cosmetics Regulation set into force in 2009 immediately became effective, in contrast to the previous (amendments of the) Cosmetics Directive which had to be translated into national law. The cause of the stable prevalence of PPD sensitizations is difficult to determine; the time period after the regulation may be too short or the enforcement of the regulation might be poor. Furthermore, other sources of exposure that are not covered by the regulation, e.g. black henna tattoos, appeared as a significant risk factor for PPD contact allergy in a population-based study. 6 The countries that contributed less, as defined in the number of individuals patch tested over the total time period, showed a wider variance of prevalence, which is indicative of chance variation. The other main observation concerning spatio-temporal variation is the variation of the overall ( ) prevalence rates of sensitization to PPD between countries, namely, from 2.5% in Denmark to 5.8% in Lithuania. These differences in prevalence between countries are not straightforward to explain, e.g. by demographic characteristics (such as ethnicity), as these should be fairly similar. Neither can they be explained by the number of tested individuals, while the number of contributing hospitals per country may have some impact in the sense that if just one department provides data, it may be an outlier in its own country. 4 Possibly trends in fashion or changes in occupational exposure are the cause of this difference. In all, the percentage of PPD sensitized females, as well as the general prevalence of PPD sensitization is highly comparable with previous studies. 3 The observed difference in the prevalence rates could be related to a greater use of hair dyes containing PPD in lower income countries compared to wealthy countries where lowsensitization dyes can be used. These low-sensitization dyes include the new ingredient methoxymethyl-p-phenylenediamine (ME-PPD) which is an alternative to PPD with a significantly reduced allergy induction risk at least according to experimental (LLNA) data. 7 Indeed, use of PPD derivatives has picked up considerably, while in Germany, for instance, PPD itself is found in only 0.3% of oxidative hair dye products. 8 Furthermore, other factors such as referral patterns of patients to patch test clinics can attribute to variations in patch test results between departments and countries. 4 In Spain, The Netherlands and Poland a major increase in the number of patch tested individuals was observed. This can be explained by an increased number of patch tested 51

13 individuals in general. However, in The Netherlands, this can be attributable to a centralization of hospital care with specialized functions of the hospitals. Therefore, more patients were patch tested in the specialized centres, which also contribute to the ESSCA network. In Germany, most, if not all, IVDK departments had ceased to test with 1% PPD pet. in 2005 due to safety concerns. This can result in a selection bias of tests recorded thereafter, as patients in whom PPD contact allergy is strongly suspected are more likely to be tested. Hence the German results from 2005 onwards were excluded. The clinical relevance of the patch test reaction is often difficult to determine. When exposure to PPD occurred in the past, and there was no history of exposure to hair dyes or a black henna tattoo with subsequent skin complaints, the source is often unclear and unreliable. Nevertheless, in the current study about half to three quarters PPD patch test reactions were clinically relevant, irrespective of occupation, and summarizing previous and current relevance. The proportion of positive reactions to PPD with occupational relevance was much lower, which is not surprising because occupational exposure occurs mainly in hairdressers, and the number of hairdressers with PPD contact allergy was low (291 of 1639 tested, Table 2). In hairdressers sensitization was very often considered relevant, although in some countries positive reactions were regarded as relevant in only three quarters of the hairdressers. However, we assume that PPD is normally relevant for hairdressers, at least in terms of elicitation, e.g. if cutting hair after dyeing. Possibly evaluating dermatologists were unaware of cross-reacting occupational material even if PPD is avoided in hairdressers, or considered protection to be perfect if gloves were worn during hair dyeing. Of course induction may have taken place by dyeing their own hair. 9 In 2008 Schnuch et al. also investigated sources of exposure in PPD-positive patients diagnosed by the IVDK network. They followed an algorithm with selection criteria according to assumed causal expsoure and other criteria such as the affected anatomical site, namely, face or hand. 10 In this study 21.5% of positive PPD patch test reactions were attributed to consumer-exposure to hair dye products. However, these data are difficult to compare with our data with regards to relevance. Patch testing additionally with the hairdressers series or testing with suspected cosmetics was a criterion for profiling in their study, for instance, while in our study we solely rely on PPD data obtained with the baseline series. 35% of the PPD-positive patients were allocated to the occupational exposure group in their study, while our data show lower percentages varying from 0.5% to 18.5%. The higher percentage in the German study can be explained by the fact that both occupational cause and hand eczema were used to define the occupational exposure group. Differences in sensitization prevalence and reaction strength of PPD patch tests between three geographical regions in Europe Thyssen et al. reported that PPD sensitization was more prevalent in central and southern European patch test centers than in the Scandinavian. 3,11 In the current study, we could 52

14 3. ESSCA results with the baseline series, : p-phenylenediamine not demonstrate a lower PPD positivity rate in the northern region compared to the other regions. This can probably be explained by differences in the included countries and patch test departments. One could suggest other grouping of the contributing countries, as socioeconomic status and ethnical groups vary widely between the countries. This renders the grouping of countries somewhat arbitrary. Thyssen et al. included in the northern region 2 departments from Denmark and 1 department from Sweden. These departments had overall low PPD positivity prevalence rates of 2.8% and 2.9% for Denmark and 2.1% for Sweden. In the current study, the northern region departments included departments in Denmark (one), Finland (two) and Lithuania (one) with overall prevalence rates of PPD sensitization of 2.5%, 3.9% and 5.8%, respectively. Although the positivity rates of PPD sensitizations in Denmark is comparable with the study of Thyssen et al., and in fact data overlap with that study, the prevalence rates of the other included countries are far higher. Reasons for the differences in PPD positivity rates between countries are partly a matter of speculation. One explanation can be ethnical differences such as hair color. Individuals in Lithuania and southern Europe have predominantly darker hair compared to the individuals in Denmark and Sweden who mostly have blond hair. We assume that people who have naturally blond hair will dye their hair more often blond when it turns gray compared to individuals with dark hair who probably will dye their hair in a dark color. It is known that dark hair dyes contain higher concentrations of PPD, which means that consumers have exposure to higher concentrations of PPD. Hence, they are more at risk of PPD sensitization. 12,13 The degree of sensitization can be demonstrated quite well by the strength of the patch test reactions at elicitation, that is whether the reaction is +, ++ or +++, or possibly a positive reaction is observed to PPD diluted by >= 2 orders of magnitude. 14 We showed a higher number of strong positive and extremely positive patch test reactions to PPD in southern Europe compared to the other regions. The strength of the elicitation reaction to PPD can be influenced by the dose of PPD at the induction. Hair dyeing with predominantly dark colors, and thus exposure to higher PPD concentrations could induce the higher number of strong positive and extremely positive patch test reactions in southern Europe. Yazar et al. investigated the compounds of consumer-available oxidative hair dye products in Sweden. They showed that Sweden had the lowest percentage of hair dye products containing PPD (16%), whereas 80% of the hair dye products contained 2,5-toluenediamine (TDA, 1,4-diamino-2-methylbenzene, CAS no ; synonym p-toluenediamine, PTD). 15 Other northern European countries such as Denmark showed that 22.2% of the investigated hair dyes contained PPD. In Germany 0.3% of the oxidative hair dyes currently contain PPD. 8 However, a study performed in Spain showed that 50% of the hair dyes contained PPD. This indicates a higher exposure to PPD in Spain among individuals who dye their hair. However, PPD may also induce an elicitation reaction by cross-reactivity to chemically related hair dyes substances, such as TDA, while TDA less often cross-reacts with PPD. 53

15 Conclusions The prevalence of PPD sensitization in referred eczema patients is high but stable over the years; no remarkable decreases of the PPD sensitization were observed within the patch test population per country and overall. In southern countries a higher number of strong positive and extremely strong patch test reactions were observed compared to northern and middle regions. This can most likely be explained by the use of darker shades of hair colors in the south. Monitoring of prevalence and reaction strength of PPD sensitization remains of great importance, as local, regional and European trends can be noticed and regulations can be adjusted. 54

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