Occupational protein contact dermatitis from shiitake mushroom and demonstration of shiitake-specific immunoglobulin E

Shiitake are popular edible mushrooms all over the world, and eating raw shiitake may lead to relatively common 'shiitake dermatitis' or toxicodermia. Workers involved in shiitake cultivation and marketing have distinct occupational respiratory and skin diseases unrelated to 'shiitake dermatitis'. There are no previous reports of protein contact dermatitis (PCD) from shiitake, and there is only 1 report of shiitake-specific immunoglobulin (Ig) E. We report 2 shiitake growers who developed work-related eczematous eruption on their hands. Both of the patients had small prick test reactions to fresh shiitake, and specific IgE to shiitake was detected in their sera by immunospot. One of the patients had a large prick test reaction to dry shiitake and also a positive wheal reaction to fresh shiitake in an open application test. Neither of the patients had noticed any symptoms of contact urticaria at work. Both of the patients had immediate IgE-mediated allergy to shiitake, and the diagnosis of occupational PCD was made. There are no commercial in vitro tests for shiitake-specific IgE. Tests for immediate allergy are important when shiitake contact dermatitis is investigated.