New relevant allergens in occupational contact dermatitis

Prof. An Goossens

Department of Dermatology

Contact-allergy Unit

University Hospital

K.U. Leuven

B-3000 Leuven

Belgium

The most important occupational contact allergens are biocides, resins, rubber-processing chemicals, metals, plants and woods, and fragrance components.

Biocides (preservatives) are increasingly causing occupational contact dermatitis. They are widely used to protect water-based products such as cosmetics, topical pharmaceuticals, household products, and industrial products such as glues, paints and cooling fluids, not to forget the cleaning products used at the workplace. However, biocides are also increasingly being incorporated in materials such as textiles, woods, packaging materials, and gloves. Especially isothiazolinone derivatives have been recently reported as allergens in this regard.

In health care workers, aldehydes and quaternary ammonium compounds used as disinfectants are gaining importance as occupational allergens.

Acrylic resins might have become the most important sources of occupational contact dermatitis from plastic materials and resins in recent years. They are widely used in various domains, such as in printing, glues, coatings, paints, but also in nail cosmetics, the latter being an important source of contact allergy in beauticians. Fortunately, the occurrence of allergic contact dermatitis from acrylic resins (and also epoxy-acrylates) in dentists and dental technicians has recently diminished due to no-touch techniques.

Epoxy resins based on diglycidyl ether of the bisfenol A type have been known as allergens for many decades. Nowadays, also newer types are found that are based on other epoxy compounds than bisfenol A, which are used to impregnate fibres used in the aircraft industry, the manufacture of electronic circuits, and wind turbine rotor blades; they may also be constituents of paints and hydraulic fluids.

In contrast to their potential for being respiratory allergens, polyurethane chemicals based on isocyanates have been increasingly recognized as skin allergens. However, in order to diagnose contact allergy, patch testing needs to be performed with the materials contacted at work, as well as with diaminodiphenyl methane, a marker for isocyanate sensitivity (MDI). Indeed, the commercially available patch test materials have been found to be inadequate.

Besides chromium, other metals such as aluminium, palladium, and even gold may cause occupational contact dermatitis. We recently observed 2 cases due to rhodium, 1 being a jeweller and another one involved in its separation (and purification) from metallic objects.

Plants and woods remain frequent occupational allergens. There is the growing interest in natural remedies, herbal products, and aromatherapy, causing not only contact dermatitis to various plant materials, but also concomitant or cross-reactivity to multiple fragrance components. The common presence of (oxidized) terpenes may account for this. An example of a terpene compound involved in occupational contact dermatitis in the industry is limonene, not only due to its presence in detergents as a fragrance component, but also widely used as an environment-friendly solvent or degreaser.

Besides, not only low-molecular weight substances but also macromolecules, i.e. proteins in plant materials, and also flours, enzymes or animal derived materials are often responsible for immunological contact urticaria and eczematous eruptions known as protein contact dermatitis, for which prick testing is the gold standard method for diagnosis. New potent protein allergen sources need to be kept in mind, such as, for example, the growing consumption of raw and smoked fish due to the influence of Japanese cuisine.

In fact, all chemicals contacted at work may act as allergens. In recent years, several chemical substances and intermediates have been described as causes of occupational contact dermatitis in the chemical and pharmaceutical industries.

Finally, lets not forget that occupational contact allergens that are first released into the air (dust, droplets, volatile substances) and then settle on the exposed skin, are the most frequent causes of airborne dermatitis. Occasionally, respiratory symptoms may be associated. The sources of the reactions may be multiple but most frequently involve plants, woods, pesticides, animal feed additives, plastic and rubber components, metals, as well as industrial and pharmaceutical chemicals.