Shiitake Mushrooms Must Be Fully Cooked Before Eating. Here’s Why.

Shiitakes are a woodland mushroom used commonly in Japanese and Chinese cuisine. The second-most common edible mushroom in the world, an estimated 10,000 tons are consumed per year.

But did you know that eating an undercooked shiitake can cause a very itchy rash in the shape of narrow strips? The rash, called flagellate dermatitis, is often found on the chest, back, legs, arms and neck. The rash typically appears within 24-48 hours after eating undercooked shiitakes.

The cause of the rash is thought to be from the toxicity of lentinan, a polysaccharide present in the roots of this mushroom. The good news is the toxicity can be neutralized by cooking the mushroom to a temperature of 266-293 degrees Fahrenheit.

The rash usually goes away on its own within a few days to several weeks. Topical steroid creams offer relief from the itchiness while the rash is resolving. No life-threatening reactions have occurred.

While cases are more common in Asia, we are beginning to see more cases in the U.S. and here locally. Due to the global popularity of Asian cuisine, commercial cultivation and farming of the shiitake, and home-growing mushroom kits, we are likely to see more cases in the future.  

The Morel (excuse the pun, we couldn’t resist) of the story is:

• Never eat shiitake mushrooms raw.
• Cook shiitakes for at least 5-7 minutes until they are tender and lightly browned.
• Mushrooms must reach an internal cooking temperature of 266-293 degrees Fahrenheit.
• To make sure shiitakes are fully cooked, insert a candy thermometer into the meaty center of the mushroom. Candy thermometers go up to temperatures of 400 degrees and are available for as little as $10 on Amazon and at local hobby stores that carry candy-making supplies.

Besides being delicious, shiitake mushrooms are very healthy. They’re high in fiber, low in calories, and a good source for B vitamins and vitamin D. Shiitakes can add a burst of flavor to eggs, sandwiches, pasta, noodles, rice and sauces. They are great combined with fish, seafood and meat. They are also a tasty side dish all on their own.

Here’s one of our favorite recipes The Kitchen Magpie.