Contact sensitisers in OD patients, IVDK 2007 – 2016: analysis of occupational groups concerned

One of the aims of this study is to describe accumulations of sensitisations to specific allergens in specific occupational groups. Therefore, we selected the 30 most frequent contact allergens among OD patients (see Tab. 3.2.1.2) and performed a comparative analysis of the proportions of occupational groups among those sensitised to the re-spective allergen (i.e. those with a positive patch test reaction) and those who are not sensitised (i.e. those with a negative patch test reaction). These comparisons are listed in Tab. 3.2.3.1 to Tab. 3.2.3.30 (see Appendix).

One has to be aware that this comparison only considers one single individual factor, namely the patient’s occupation. However, risk of sensitisation is not only attributed to occupation, but also (in some cases even more) to age, gender etc. Hence, even sig-nificant differences are to be regarded as a starting point for a professional analysis rather than as irrevocable facts. Existing knowledge of occupational exposure and al-lergens (see Section 1.4.3) has to be considered when interpreting this data.

Nickel sensitisation occurs preferredly in females and is acquired by wearing costume jewellery [Uter et al. 2003a; for more information also see Section 1.4.2.5)]. Accord-ingly, occupational groups with female predominance like nurses, hairdressers, clean-ers, cosmeticians etc. (see Tab. 3.2.2.2) are over-represented among patients sensi-tised to nickel (Tab. 3.2.3.1), while the opposite is true for typical male occupations such as mechanics, metal workers etc.

Fragrance allergy also occurs more frequently in women than in men [Uter et al.

2015a]. In addition, geriatric nurses seem to have a particular occupational risk of fra-grance sensitisation, probably due to their intense and repetitive exposure to cosmetics and body care products of their clients [Schubert et al. 2017; for more information, see Section 1.4.2.4)]. This is reflected in Tab. 3.2.3.2, where not only geriatric nurses are over-represented among those reacting to fragrance mix I, but also other occupational groups with a higher share of women. Similar findings are made with fragrance mix II

(Tab. 3.2.3.9) and the fragrances hydroxyisohexyl 3-cyclohexene carboxaldehyde (Tab. 3.2.3.14), and ylang ylang oil (Tab. 3.2.3.25).

Among patients sensitised to MCI/MI, there were more hairdressers, geriatric nurses, and painters (Tab. 3.2.3.4), compared to those not sensitised to MCI/MI. In hairdress-ers and geriatric nurses, the relevant exposures probably are hair cosmetics and body care products, and in painters, water-based wall paints (see Section 1.4.2.6). Among those reacting to MI (Tab. 3.2.3.7) painters were over-represented, too, as well as cos-meticians (personal care workers). In all of these cases, it has to be considered that in recent years, there has been a cosmetic-induced epidemic of sensitisation to MI which has also led to increased reactions frequencies to MCI/MI (see Section 1.4.2.6).

Thiurams are used as vulcanizing agents in rubber glove production, and are the most frequent contact allergens in patients suffering from rubber glove dermatitis (see Sec-tion 1.4.2.8). Accordingly, occupaSec-tional groups in which elastic protective gloves are worn are over-represented among patients sensitised to thiurams. These are cleaners, cooks and food processors, construction workers, medical professions, geriatric nurses etc. (Tab. 3.2.3.6).

Concerning potassium dichromate (Tab. 3.2.3.8), significantly more construction work-ers are among those with a positive reaction, compared to those with a negative reac-tion. However, this is not an indicator of a current problem. Dichromate has been the most important occupational allergen in the building trade for decades, and hence we find a lot of sensitisations which have been acquired years ago (see also Sections 1.4.2.5 and 1.4.3.2)

Among patients sensitised to colophony, there were significantly more metal workers, office clerks, and gardeners than among those without patch test reaction to colophony (Tab. 3.2.3.10). As described in section 1.4.2.7, allergens present in colophony also occur in distilled tall oil, which is a frequently used basic material for water-based met-alworking fluids. Colophony allergens also may be present in recycled paper, and in woods. These exposures may (at least partly) explain the accumulation of the above-mentioned occupational groups among patients sensitised to colophony.

With methyldibromo glutaronitrile (MDBGN) (Tab. 3.2.3.11 and Tab. 3.2.3.12), the sit-uation is special. Using an adequate test concentration, i.e. MDBGN 0.2% in petrola-tum, we find a significantly increased proportion of geriatric nurses among those sitised. As MDBGN is prohibited in cosmetics and body care products since 2008, sen-sitisation by this route must have been acquired before. Unfortunately, MDBGN has to be tested at 0.3% in petrolatum since spring 2016 because the preferred test prepara-tion (0.2%) is no longer available. Since then, reacprepara-tion frequencies have more than doubled – although there is no exposure of the general population. From earlier inves-tigations it is well-known that with the higher test concentration many false-positive reactions are elicited [Schnuch et al. 2018].

Contact allergy to epoxy resin is an important issue in the construction industry. As mentioned in Section 1.4.2.3, not only the resins, but also hardeners and reactive dil-uents may cause allergic reactions. Among patients sensitised to epoxy resin, occu-pational groups from the building trade as well as painters are more frequently men-tioned than among those with a negative epoxy resin patch test (Tab. 3.2.3.13). The

same applies to 1,6-hexanediol diglycidylether, a frequently used reactive diluent in epoxy resins systems (Tab. 3.2.3.23). In addition, plastic-product machine operators and engineers are over-represented. In these groups, an occupational exposure seems plausible or at least possible. However, we have no explanation for the finding that “patients with occupations with undetermined exposure”, which are all profession-als, in whom the professional title allows no conclusion regarding the occupational ex-posure (students, trainee, unskilled workers), are over-represented among those sen-sitised to epoxy resin.

At a first glance, it may seem plausible that there are more health care workers among those reacting povidone iodine (a skin disinfectant) than among those with a negative patch test to povidone iodine (Tab. 3.2.3.14). However, one has to consider that pov-idone iodine 10% aqu., which is the most frequently used povpov-idone iodine patch test preparation, belongs to the so-called problematic allergens with frequent false-positive reactions (see Section 1.2, Tab. 1.2.2).

Exposure to hair dyes is by far the most frequent source of contact with and sensitisa-tion to p-phenylenediamine (PPD) and toluene-2,5-diamine. Accordingly, PPD and tol-uene-2,5-diamine are typical occupational allergens in hairdressers (Tab. 3.2.3.17 and Tab. 3.2.3.18) (see also Section 1.4.3.6).

Among those sensitised to formaldehyde, there are significantly more metal workers than among those without patch test reaction to formaldehyde (Tab. 3.2.3.20). Water-based metal working fluids are preserved with formaldehyde releasers, and most metal workers do have permanent skin contact with these metalworking fluids because wear-ing gloves is prohibited when workwear-ing at machines with rotatwear-ing tools (see Sections 1.4.2.6 and 1.4.3.8).

1,3-Diphenylguanidine is a rubber ingredient which has gained increasing allergologi-cal attention as contact allergen in mediallergologi-cal gloves (see Section 1.4.2.8). Accordingly, we find more medical doctors among those sensitised to 1,3-dihenylguanidine (Tab.

3.2.3.21). Other health care professionals seem to be less concerned; however, in this occupational group, more cases of contact sensitisation to thiurams are observed (Tab.

3.2.3.6).

Iodopropynyl butylcarbamate (IPBC) is being used as preservative in body care prod-ucts as well as in industrial applications like wood preservation or in metalworking fluids [Schnuch et al. 2002c]. However, only metal workers exposed to metalworking fluids are over-represented among those sensitised to IPBC, while geriatric nurses are not (Tab. 3.2.3.24). Obviously, the exposure to IPBC by metalworking fluids bears a greater risk of sensitisation than IPBC exposure by body care products.

As mentioned in Section 1.4.2.7, oil of turpentine was the classical occupational aller-gen in painters and varnishers until the 1960s. Nowadays, oil of turpentine is rarely used in this branch. However, it may be present in oil colours for artist painters. This is reflected in Tab. 3.2.3.25. While painters and varnishers are not over-represented among patients sensitised to oil of turpentine, we found an increased proportion of artists (who are, however, only a small group).

Benzoyl peroxide 1% pet. is a so-called problematic allergen with frequent false-posi-tive reactions (see Section 1.2, Tab. 1.2.2). Nevertheless, it has been identified to be a relevant occupational contact allergen in dental technicians (see section1.4.3.3). Re-markably, among those reacting to benzoyl peroxide, not dental technicians, but den-tists are over-represented (Tab. 3.2.3.27). This constellation is hard to explain. Either there are dental assistants (who are subsumed in the group “dentists”) who do dental technicians’ work or some dental technicians are inaccurately documented as dentists.

Monoethanolamine is used as rust preventing agent with emulsifying properties in wa-ter-based metalworking fluids and is an important allergen in this context (see Section 1.4.3.8). Accordingly, we found an increased proportion of metal workers among pa-tients sensitised to monoethanolamine (Tab. 3.2.3.29). Monoethanolamine may also occur in hair dyes, and hence it is being tested as part of the hairdressers’ series.

However, hairdressers were significantly under-represented among those sensitised to monoethanolamine, which may indicate that it is not a significant allergological prob-lem in this context.

Ammonium persulfate is a frequently used ingredient of hair bleaching agents and a well-known hairdresser allergen (see Section 1.4.3.6). As ammonium persulfate may also cause airway allergy, improved product formulations (cream instead of powder) have been developed to prevent airborne exposure. However, it seems like this had no significant impact on contact sensitisation by skin exposure [Uter et al. 2014b]. As can be seen from table Tab. 3.2.3.30, there are significantly more hairdressers among patients sensitised to ammonium persulfate than among those not reacting to it.

Positive patch test reactions to 4,4'-diaminodiphenylmethane (4,4’-methylenedianiline;

MDA) may indicate contact sensitisation to MDA itself or be the expression of immu-nological cross reactivity [Geier and Lessmann 2017]. Nowadays, there is no longer any relevant (occupational) exposure to MDA, because it is a carcinogenic substance.

Nevertheless, positive patch test reactions are frequently observed. In most cases, these reactions indicate contact allergy to so-called “para-substances”, which are com-pounds with structural similarity to p-phenylenediamine. Based on immunological cross-reactivity, these patients, who are primarily sensitised to p-phenylenediamine, do also react to other chemically related compounds, among them MDA. In addition, sensitisation to diphenylmethane-4,4’-diisocyanate (MDI) may lead to a positive patch test reaction to MDA, based on the transformation of MDI to MDA on and/or in the skin [Geier and Lessmann 2017; Hamada et al. 2017]. Correspondingly, an increased pro-portion of hairdressers (exposed to PPD in hair dyes), construction workers and paint-ers (potentially exposed to MDI from polyurethane foams or lacqupaint-ers) might be over-represented among those reacting to MDA. While we indeed found an increased pro-portion of constructions workers and painters among these patients, hairdressers were not over-represented (Tab. 3.2.3.31).

3.3. Estimation of annual incidences of contact sensitisation