Methods: Skin prick tests (SPTs) were performed with fresh cow’s milk-derived products. Specific IgE (sIgE) assays were performed using the ImmunoCAP system (Thermofisher Scientific, Sweeden).
Results: A 35-year-old patient with a history of atopy had worked as a cheesemaker (using cow’s milk) for 3 years. He developed severe urticaria on the arms and neck following direct or indirect contact with dairy products that he handled at work. Most recently, he developed eczema on the back of the forearms at the end of a working week. Skin disorders always resolved during vacations. SPTs with fresh cow's milk, whey, butter and cream were all positive. SIgE assays were positive for c cow’s milk (56.70 kUA/l) and its components alphalactalbumin (1.35 kUA/l), betalactoglobulin (36.40 kUA/l) and casein (23.40 kUA/l). The patient reported that his consumption of dairy products never triggered the symptoms of food allergy. This was confirmed by a negative oral challenge test with 298 ml of fresh cow’s milk.
Conclusions: To the best of our knowledge, this is the first ever report of occupational contact urticaria to cow’s milk in the absence of CMA and including component-resolved exploration. The present case demonstrates that food allergy and sIgE-positive skin allergy operate through different pathways.