A 54-year-old man showed up at a Swiss emergency room with long red streaks spreading across his body, as if he had been whipped. Oddly, they did not itch, and he denied scratching. Streaks like these can point to a chemotherapy reaction or autoimmune disease, but a dermatologist found the answer in his diet: undercooked shiitake mushrooms he had eaten four days before the rash appeared.
The case, published in July 2026 in Swiss Medical Weekly by doctors at Geneva University Hospitals, adds to a growing set of reports urging clinicians who see whip-mark streaks to ask a simple question: what did you eat?
