An Asian mushroom savoured by Japanese emperors for centuries and increasingly used by European consumers in cooking could cause a skin reaction in people sensitive to the polysaccharide.
Grown on oak or sweetgum logs, shiitake is now the second most popular mushroom it the world - after the button - and used for more than a 1000 years in Asian culture, the mushrooms are native to Japan, China, Taiwan, and Korea. But enjoyment of this increasingly popular European ingredient may be somewhat dampened by striated, lash-like reddening of the skin.
According to the German food authority BfR, lash-like reddening of skin on the torso, arms, legs and nape of the neck has been observed in the past particularly after the consumption of inadequately cooked mushrooms. The recommendation was, therefore, only to eat Shiitake mushrooms if they had been thoroughly cooked or fried.
But more recent reports from doctors point out that the form of cooking does not affect health disorders in people who are in any case sensitive. Shiitake dermatitis also developed in consumers who had eaten well-cooked or fried mushroom dishes.
"BfR advises keeping an eye open for possible intolerance reactions and to refrain from eating any more of this delicacy as soon as the first signs are observed. Since ultraviolet light may exacerbate the reaction, the skin areas concerned should not be exposed to the sun either," said the food authority this week.
In order to build a bigger picture of this potentially irritating food reaction, the BfR is centralising all information at the Federal Institute for Risk Assessment.
Japan is a key producer of shitiake, and the vegetable has become the country's number one agricultural export with gross sales of a billion dollars per year.
A Project run by the Minnesota department of agriculture - Eagle Bluff - claims that studies from Japan suggest shiitake mushrooms are more nutritious than most mushroom species and may play a role in lowering blood cholesterol.