Systemic allergic contact dermatitis due to consumption of raw shiitake mushroom.

Shiitake (Lentinus edodes) is a mushroom that is very popular in Asian cuisine. After ingestion of the raw fungus, dermatitis may occur in rare cases, and is commonly assumed to be a toxic reaction. We report a 52-year-old man who developed a generalized pruritic papulovesicular eruption 2 weeks after daily consumption of uncooked shiitake mushrooms. Prick-to-prick and scratch tests with uncooked mushrooms resulted in an eczematous reaction at 24 h that peaked at 72 h and persisted for 1 week. In contrast, no cutaneous reactions could be elicited in 20 healthy people. We conclude that our patient had systemic allergic contact dermatitis due to consumption of raw shiitake mushroom.