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Enjoyment with unpleasant consequences

10/2004, 19.08.2004

Skin reactions may occur after eating Shiitake mushrooms

The Shiitake mushroom (Lentinus edodes) is popular in Germany as an edible mushroom. It is grown and eaten in large quantities. However, in the case of particularly sensitive people this culinary enjoyment may be somewhat dampened later by striated, lash-like reddening of the skin. The trigger of this rare, in some cases severe, skin reaction is probably a natural ingredient in this kind of mushroom.

Shiitake mushrooms are not just popular because of their excellent flavour and aroma. They are also said to have an all round beneficial effect on health. All the same, for a few people the consumption of these mushrooms has unpleasant health consequences. Just a few hours after consuming them, Shiitake or flagellar dermatitis occurs. This is probably a hypersensitivity reaction to the polysaccharide, lentinan, contained in the mushroom.

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. However, 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. All the same, only a few cases of this have been observed in Germany up to now.

After consuming Shiitake mushrooms, 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.

In the case of patients with flagellar dermatitis, doctors should first establish whether the skin reactions are possibly the result of eating Shiitake mushrooms. For the purposes of central recording BfR asks for cases of this kind to be notified to the Federal Institute for Risk Assessment.

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