Oct 17, 2023 13:00:00

A man who ate undercooked shiitake mushrooms developed 'shiitake dermatitis,' which causes a rash that looks like a whiplash.

Shiitake is a mushroom that represents Japan, and in recent years it has become available in Western countries outside of Asia. Meanwhile, a 72-year-old man living in Switzerland ate undercooked shiitake mushrooms and developed a disease called ' shiitake dermatitis ,' which caused a rash on his body that looked like he had been whipped.・Reported by doctors at Geneva University Hospital.

Shiitake Dermatitis | NEJM
https://www.nejm.org/doi/full/10.1056/NEJMicm2304409

Undercooking Shiitake Risks This Intensely Itchy Rash
https://www.newsweek.com/shiitake-mushrooms-rash-dermatitis-medicine-1834444

Man gets rare 'shiitake dermatitis' from undercooked mushrooms | Live Science
https://www.livescience.com/health/viruses-infections-disease/man-gets-rare-shiitake-dermatitis-from-undercooked-mushrooms

Two days after eating a meal using shiitake mushrooms, the 72-year-old man reported developed a rash (erythema) all over his back that looked like he had been whipped. This erythema was accompanied by severe itching, which made it difficult to even sleep.

The photo below is a photograph of the erythema that actually appeared on a man's back. You can see that there is a striped erythema all over the back.

When doctors examined the erythema, they found that there was no strong scratching or rubbing of the skin, and there were no signs that the lymph nodes were swollen due to bacterial or viral infection. Doctors then interviewed the man about what he had eaten in the past few days and concluded that he had developed 'shiitake dermatitis' caused by the shiitake mushrooms he had eaten two days earlier.

Shiitake dermatitis is a disease first reported in Japan in 1977, and it occurs in about 2% of people who eat raw or semi-raw shiitake mushrooms, as well as those who drink rehydrated dried shiitake mushrooms or eat shiitake processed products. There are also cases where people develop symptoms. Cases have been reported primarily in Japan and China, but also in other regions such as Europe and North America.

The exact mechanism by which shiitake dermatitis occurs has not been determined, but a leading hypothesis is that it is an immune-mediated hypersensitivity reaction to the polysaccharide

lentinan found in shiitake. Lentinan promotes the release of a physiologically active substance called interleukin-1 , which causes inflammation, and is said to induce dilation of blood vessels and rashes. Lentinan is broken down by heat, so doctors point out that shiitake dermatitis will not occur if shiitake mushrooms are thoroughly cooked above 145 degrees Celsius.

Shiitake dermatitis is not a life-threatening condition and will heal on its own over time, but doctors prescribed steroids applied to the back and oral antihistamines to alleviate the symptoms. He also advised men to heat shiitake mushrooms thoroughly before eating them.

Although the man's symptoms had eased considerably when he was examined two weeks later, it is reported that pigmentation, which is common in post-inflammatory skin, remained.