His skin looked like shiitake.

A man had to be hospitalized after an adverse reaction to eating undercooked mushrooms caused him to contract a painful-looking skin condition.

His fungus-induced affliction was detailed recently in “The New England Journal Of Medicine.”

According to the case study, the unnamed 72-year-old patient had reportedly “prepared and eaten a meal containing shiitake mushrooms,” earthy, meaty fungi that’s a signature ingredient in many East Asian cuisines.

The fungi-loving gourmand didn’t think anything of it until two days later, when he developed an “itchy, linear rash across his back,” which was so painful that it impeded his sleep, LiveScience reported.

Accompanying photos show the patient’s back and buttocks, which are streaked with long red welts as if he’d been flogged.

Alarmed, the poor soul reported to the doctor, who diagnosed him with “shiitake dermatitis,” which occurs when someone eats raw or undercooked mushrooms.

First recorded in Japan in 1977, the ailment is most common in Asia, where shiitakes are most widely consumed but has also been reported in Europe and North and South America as well.

The rashes are specifically caused by lentinan, a carbohydrate that sends out chemical messengers which cause inflammation like a low-grade “The Last Of Us” infection.

Along with these unsightly legions, shiitake dermatitis patients can also experience swelling, fever, diarrhea, tingling of the lips and hands/feet, and discomfort swallowing.

Thankfully, Letinan is broken down when heated, meaning that the condition can be avoided by simply cooking the shiitakes.

“Shiitake dermatitis doesn’t occur when the ingested mushrooms are thoroughly cooked at temperatures surpassing 145 degrees Celsius [293 degrees Farenheit],” said Eglė Janušonytė, a co-author of the case and dermatology resident at Geneva University Hospitals in Switzerland.

The man was subsequently administered a course of steroids and antihistamines to relieve his itching while the rash eventually went away on its own.

Doctors also warned the shroom sashimi enthusiast to “fully cook shiitake mushrooms in the future.”