No one suspects a mushroom when a rash like this appears.
The marks appeared on a woman’s back several days after eating shiitake, forming parallel red lines that looked like lash marks. It was neither a common allergy nor an infection: doctors identified a reaction called shiitake dermatitis, caused by a compound called lentinan that is released when the mushroom is eaten raw or undercooked.
The phenomenon was first described in 1977 and continues to surprise those who experience it, because the rash can take up to five days to appear and almost a month to disappear completely. Similar cases documented in medical journals show the same pattern in different people around the world, always with the same culprit: an ingredient that many consider harmless in their cooking.
