A 47-year-old woman arrived at an emergency room in New York with an itchy rash on her back that had persisted for two days. The rash, which initially appeared as isolated inflamed spots on her upper back, spread to her lower back in irregular stripes resembling whip marks, despite treatment with steroids and antihistamines at an urgent care center.
The cause? Shiitake mushrooms. The woman had eaten a large serving of the fungi two days before the rash appeared.
Shiitake mushroom dermatitis, though rare, typically occurs when the mushrooms are eaten raw or undercooked. The condition is caused by a toxin called lentinan, which triggers an inflammatory response in the skin. The rash usually resolves on its own within two to three weeks, but can be treated with topical steroids.