Shiitake dermatitis is a rare adverse cutaneous reaction to the ingestion of raw or undercooked shiitake mushrooms (Lentinula edodes). We report the case of a patient who developed a striking linear flagellate dermatitis without urticaria three days after returning from a trip from Tokyo where he had eaten shiitake mushrooms. The rash resolved after two weeks with topical corticosteroids and antihistamines given for symptomatic relief. Shiitake dermatitis is thought to be either a toxic or hypersensitivity reaction to lentinan, a heat-inactivated polysaccharide found in the cell walls of shiitake mushrooms. Although this mushroom is widely consumed in Eastern Asia, with the increasing globalisation of cuisine and travel, cases are likely to become more common in the Western world.