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Ever-changing exposure to contact allergens, partly due to statutory directives (e.g. nickel, chromate, methyldibromo glutaronitrile) or recommendations from industrial associations (e.g. hydroxyisohexyl 3-cyclohexene carboxaldehyde), requires on-going epidemiologic surveillance of contact allergy. In this paper, the current state with special focus in fragrances and preservatives is described on the basis of data of the Information Network of Departments of Dermatology (IVDK) of the year 2010. In 2010, 12,574 patients were patch tested in the dermatology departments belonging to the IVDK. Nickel is still the most frequent contact allergen. However the continuously improved EU nickel directive already has some beneficial effect; sensitization frequency in young women is dropping. In Germany, chromate-reduced cement has been in use now for several years, leading to a decline in chromate sensitization in brick-layers. Two fragrance mixes are part of the German baseline series; they are still relevant. The most important fragrances in these mixes still are oak moss absolute and hydroxyisohexyl 3-cyclohexene carboxaldehyde. However, in relation to these leading allergens, sensitization frequency to other fragrances contained in the mixes seems to be increasing. Among the preservatives, MCI/MI has not lost its importance as contact allergen, in contrast to MDBGN. Sources of MCI/MI sensitization obviously are increasingly found in occupational context. Methylisothiazolinone is a significant allergen in occupational settings, and less frequently in body care products.

A broad spectrum of various substances may cause occupational allergic contact dermatitis. Often, it is difficult to identify potentially or truly relevant allergens at the workplace. Therefore, the consulting physician must have a comprehensive knowledge of possible allergens in different occupations to perform specific diagnostics and to initiate efficient secondary prevention by allergen avoidance. In this review, we give some practically relevant general comments on patch testing in occupational dermatitis, followed by a discussion of important occupational allergens in those occupational groups most frequently affected by occupational dermatitis. Finally, recommendations on which allergens should be tested in the respective occupational groups are given or reported from the literature.

The selection of the most important contact allergens is subject to a continuous change. Several factors may influence the sensitization rates and thus the decision, which substances to include in the standard series of the most frequent allergens. The Information Network of Departments of Dermatology adds substances of interest for a certain time period to the standard series in order to evaluate parameters such as sensitization rate, grade of reaction, and clinical relevance of positive reactions. In 6 testing periods starting in 1996, 13 test substances were evaluated. Due to the results, propolis, compositae mix, and bufexamac were included in the standard series in 1999, while lyral was added in 2002. Sorbitansesquioleat, dispers blue mix, and iodopropynyl butylcarbamate are under further discussion. Substances such as glutaraldehyde and p-aminoazobenzole should be tested in certain risk groups only, whereas the steroids budesonide and tixocortol should be tested when clinically suspected.

Background: In the early 1990s, the prevalence of nickel contact allergy was high-almost 20% on a population level, and some 40% in contact dermatitis patients. Around that time, nickel exposure was starting to be regulated., Patients/methods: Descriptive and bivariate analyses of patch test results of all patients tested with nickel sulfate (5% pet.) in the departments joining the Network of Departments of Dermatology (IVDK) 1992-2001 (n=82,991, women: 52,709; men: 30,282). The annual frequency of sensitization to nickel was analyzed in women and men in four age subgroups (<31/31 to <44/44 to 58= or >58)., Results: In young women less than 31 (n=13.909) the prevalence of contact allergy to nickel decreased significantly from 36.7% in 1992 to 25.8% in 2001. In young men in the same age group (n=7087), the prevalence dropped from 8.9% in 1992 to 5.2% in 2001., Conclusions: The observed decline indicates that measures to limit the release of nickel from costume jewelry helped reduce the prevalence of nickel allergy. In general term, allergen elimination or reduction is an effective primary prevention strategy which does not depend on individual behavior modifications.