Warning over seriously disturbing reactions to undercooked mushrooms

Mushrooms are fickle friends indeed. The humble chestnut mushroom is packed with nutrition and tastes great, while the fantasy-looking fly agaric can both make you see God and send you to meet him.

There are countless varieties both edible and otherwise, and some are attached to particular cooking instructions designed to keep you safe.

If you leave your shrooms undercooked, even the non-toxic ones could cause you some grief.

An article published in the New England Journal of Medicine on October 11th 2023 sought to raise awareness over the effects of undercooked mushrooms.

It details how a 72-year-old man was admitted to A&E with 'an itchy, linear rash across his back' – the image makes for unsettling viewing. It looks like either a cat-o-nine-tails or a wolverine has been at the guy’s back.

The rash is no joke (The New England Journal of Medicine/ Eglė Janušonytė/ Jöri Pünchera)

The rash developed within two days of the man eating shiitake mushrooms for dinner, and he had no signs of a viral or bacterial infection.

He was suffering from the aptly-named condition known as Shiitake Dermatitis.

The Brazilian Society of Dermatology describes the condition as ‘ a skin eruption that resembles whiplash marks and occurs after consumption of raw shiitake mushrooms'.

"It is caused by a toxic reaction to lentinan, a thermolabil polysaccharide which decomposes upon heating."

In other words, the lentinan should break down when the mushroom is properly cooked.

It was first identified by Takehiko Nakamura after observing '51 patients with shiitake dermatitis’.

"In 1992, Nakamura made a prediction that, in the future, there would be an increase in the occurrence of shiitake dermatitis, due to the growing popularity of this delicacy in the occidental diet.

"Indeed, the world's mushroom industry markets more than two million tons of mushrooms per year and is still expanding. Today, shiitake mushrooms are the second most produced edible mushrooms worldwide," the Official publication of the Brazilian Society of Dermatology continues.

Shiitake are a staple in Japanese cuisine (Joff Lee/Getty Images)

Given shiitake mushrooms’ popularity around the world, it’s unsurprising that there have been reported cases all over.

The Brazilian Society of Dermatology said the condition is very treatable and should be 'resolved completely in about 10 days'.

In the case of the 72-year-old, he was given antihistamines and topical steroids before making a full recovery.