Occupational Contact Urticaria

The preparation of food in restaurant kitchens carries a high risk of occupational dermatoses. Analysis of 33 cases revealed four different etiological types. Simple irritant dermatitis was rare (2 cases), plain contact dermatitis was more common (6 cases). Fifteen patients had relevant patch tests and scratch tests; ten had positive scratch tests only to explain the cause of their dermatitis. The last type was termed protein contact dermatitis. The major type IV allergens incriminated were metals, onion and garlic. The major proteinaceous allergens indicated by history and test results were fish and shell-fish. Open patch tests with the incriminated foods may cause erythema or oedema on normal skin after 20 minutes. Previously eczematous, now normal looking, skin often responds with a crop of dyshidrotic vesicles preceded by erythema and itching 30 minutes after the application of an open test. Examination for specific IgE is not always positive in such cases. Inhalant allergy was rare. The results indicate that food handlers are sensitized by the protein they touch, and then react to later contact with the proteins. Protein contact dermatitis is similarly common among veterinary surgeons, while the importance in other occupational groups remains to be studied.

Baking and food industry workers are exposed to several powdered Aspergillus-derived enzymes with carbohydrate-cleaving activity that are commonly used to enhance baked products. We describe a retrospective study of sensitization to fungal alpha-amylase and cellulase on bakers. Five bakers in whom respiratory allergy symptoms developed when they were exposed to bread "improvers" that contained fungal alpha-amylase and cellulase were investigated by in vivo and in vitro tests. Type I hypersensitivity to these enzymes was demonstrated in the five patients by means of skin testing, histamine release test, positive reverse enzyme-immunoassay for specific IgE antibodies, and bronchial provocation test response to alpha-amylase or cellulase or both. Isolated immediate and dual responses to the bronchial challenge tests with these enzymes were observed. Immunoblot analysis with use of a pooled serum identified IgE-binding components in both enzymes. In the reverse-enzyme immunoassay-inhibition assays cross-reactivity between alpha-amylase and cellulase was not found, but some degree of cross-reactivity between alpha-amylase and A. oryzae, and between cellulase and A. niger was demonstrated. Four of the patients were also sensitized to cereal flour. Aspergillus-derived enzymes used as flour additives can elicit IgE-mediated respiratory allergy, and this fact has to be considered in the diagnosis and clinical management of bakers' asthma.

A complementary DNA encoding a pollen allergen from white birch (Betula verrucosa) that was isolated from a pollen complementary DNA library with serum immunoglobulin E from a birch pollen-allergic individual revealed significant sequence homology to profilins. The recombinant protein showed high affinity to poly-L-proline. Immunoglobulin E antibodies from allergic individuals bound to natural and recombinant birch profilin and also to human profilin. In addition, birch and human profilin induced histamine release from blood basophils of profilin-allergic individuals, but not of individuals sensitized to other plant allergens. The structural similarity of conserved proteins might therefore be responsible for maintaining immunoglobulin E antibody titers in type I allergy.