Consumption of raw or slightly cooked shiitake mushrooms can cause "an erythematous, micro-papular, streaky, extremely pruriginous rash" that occurs all over the body including face and scalp, which appears about 48 hours after consumption and disappears after 10 days. This effect, caused by the toxin lentinan, is well known in Asia, but can be unfamiliar to European physicians.[11] It occurs in roughly 1 in 50 people, and thorough cooking eliminates the effect.[citation needed]"
"Shiitake Dermatitis Syndrome – Toxic and Allergic Reactions to Raw and Undercooked Shiitake
For affected individuals, a rash usually begins about 48 hours after consumption of raw or undercooked Shiitake and lasts for about 10 days. It is a toxic, not an allergic, reaction and is believed to result from lentinan, a starch-like polysaccharide, triggering blood vessels to dilate and leak small amounts of inflammatory compounds just beneath the skin. The rash typically begins as red areas that neither hurt nor itch. Soon red blisters form and then harden over the red regions but the rash is not initially itchy like a poison oak rash would be at that point. The red streaks then turn to purple raised welts which persist for days. The purple welts make the victim appear to have been flogged or to have been vigorously scratching a poison oak rash. The syndrome was long thought to be restricted to Asia since most of the world's production of Shiitake [Lentinula edodes (Berk.) Pegler] occurs in Asia. However, a case has recently been reported from Portland, Oregon and there may have been other cases that were not diagnosed. Clinically the rash resembles flagellate dermatitis caused by Bleomycin, a sulfur-containing polypeptide derived from Streptomyces verticillus. Lentinan is decomposed upon heating and so it is only consumption of raw or partially cooked Shiitake that poses a problem. Only 2% or less of the population is likely to be affected.
While Shiitake dermatitis itself is a toxic reaction, not an immune-stimulated allergic reaction, consumption a large amounts of raw Shiitake in individuals who would otherwise be unaffected, can lead to an allergic response. Sensitized individuals react strongly when pricked with raw Shiitake but not with cooked Shiitake, indicating that they have developed an allergy. Some workers in Shiitake grow houses develop an eczema-like rash due to Shiitake specific immunoglobulin. There are also documented cases of allergic and chronic hypersensitivity pneumonitis induced by spores of Shiitake."
The itchiness is really exceptionally severe. Local doctors seem not too well aware about appropriate treatment; mine approached the syndrome as an allergy. Perhaps I should have taken some information along with me to the doctor.
ReplyDeleteI have this rash too. Took me a while to figure out what it was though. Its horrible, looks horrendous and I just want to be normal. Shiitake mushrooms should come with a warning. Its been quite distressing.
ReplyDeleteIt's awful. I have now had it twice and am VERY careful when ordering mushroom dishes and always make sure there are no shiitakes even if they are cooked. I am not planning to live through 2 weeks of hell again thanks. I notified Vivo of my experience and they have now taken shiitakes off their menu as they don't want to risk it happening to another person (or their staff being sensitised from contact with them).
ReplyDeleteHello, I was wondering if you could tell for how many days this terrible itching continues? There's not that much precise symptom information about this reaction. I can't sleep like this!
ReplyDeleteHI. I can't remember exactly how long, but I think it was bad for about a week, and took about 2 weeks from start to finish. As I recall towards the end of the first week it started to get better. But it was very hard not to literally claw at my skin, and I'd wake up at night scratching myself. Also if I ran, and got hot and sweaty, it would feel much worse and would blister more. It is very very unpleasant.
DeleteI am glad to get this information as there is little personal discussions online about this horrible condition. Today is day five for me after eating the mushrooms raw in a salad both Friday and Saturday. Sunday I woke up with a red rash on one side of the back of my neck and a red hand. Since then it covers my body and has spared my feet. Appeared on the left temple today so I am watching it to make sure it stays away from my eyes. I have found no cream or soap or anything to get relief from the intense itching. My doctor has me on a Medrol prednisone pk. b it from what Ived read it does no good. How long will this rash keep spreading?
ReplyDeleteFor me it got progressively worse during the first week and then dissipated in the second week. Nothing really helps, but a cortisone cream can help to relieve the itchy/burny feeling. I remember waking at night finding I was scratching and clawing at myself.
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