INSIDER – A 72-year-old man went to the emergency room with inflamed red streaks all over his back and upper buttocks and said that the rash was so itchy and painful that he couldn’t sleep, according to a medical case report published on October 12 in the New England Journal of Medicine.
When doctors found that the man’s lymph nodes were not swollen, a sign that the body is fighting an infection, and he did not have dermographism, a condition that leaves raised marks on the skin when pressure is applied, or any other serious skin conditions, they asked about what he had eaten recently, the report said.
He was diagnosed with shiitake dermatitis after doctors learned he had eaten a meal containing shiitake mushrooms two days earlier.
Shiitake dermatitis is caused by a toxic reaction to lentinan, a soluble fiber in shiitake mushrooms that decomposes when heated, making them safe to eat if properly cooked.
CORRECTION: An earlier version of this post attributed this story to CBS NEWS. It was actually published by INSIDER. We regret the error.