Food Poisoning From Shiitake

Clusters of shiitake mushrooms growing on logs.
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Shiitake mushrooms, a traditional food also used as a medicine in Asian cultures, are the third most popular mushroom in the United States, according to ScienceDaily. The mushrooms, which grow on oak logs, are low in calories but high in minerals such as potassium and zinc. Shiitake mushrooms, unlike some mushroom varieties, are not poisonous. Any processed food, however, can become contaminated at some point in the growing, processing or preparation process. Some people also develop allergies to shiitake mushrooms that produce symptoms very similar to, and possibly confused with, food poisoning.

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Contamination During Growing

Shiitake mushrooms can become contaminated by infected water or animal droppings while growing. Salmonella and other bacteria such as E. coli can sicken people who eat food contaminated with the bacteria. To avoid food poisoning, wash shiitake mushrooms carefully under running water before eating them. Vegetable washes may not remove contaminants from mushrooms as well as fresh, running water, Health Canada states. Most cases of food poisoning cause vomiting, diarrhea, abdominal pain and sometimes fever.


Contamination During Processing

Bacterial contamination can occur during processing or as a result of faulty packaging. In 2002, tins of Dragon Boat Shiitake Mushrooms were found to have defects in the seams that could allow bacteria to infiltrate the tins. Fresh shiitake mushrooms packaged in unrefrigerated airtight containers can be sources of botulism, caused by Clostridium botulinum, a bacterium that multiples in areas with little oxygen supply. When buying fresh mushrooms, look for packaging that has holes in it to allow air to circulate, Health Canada advises. Store fresh mushrooms in the refrigerator after purchasing for up to five days. Symptoms of botulism, which start between 12 and 36 hours after eating a contaminated product, include nausea, vomiting, stomach pain, difficulty swallowing or speaking, facial weakness, and muscle paralysis. Seek immediate medical attention if you suspect botulism.


Contamination During Cooking

If food handlers carry certain intestinal bacteria or viruses, they can pass them on to others by not thoroughly washing their hands before handling the mushrooms. While cooking may destroy some bacteria or viruses, shiitake mushrooms are often served as part of a salad or other uncooked dish. Since you can't smell or taste bacteria, it's impossible to know if the mushrooms will make you sick. Vomiting, diarrhea, fever or abdominal pain after eating shiitake mushrooms requires medical investigation for possible food poisoning.

Allergic Reactions

Allergic reactions to shiitake mushrooms can be confused with food poisoning, since the symptoms may be similar. Ingesting more than 15 g to 20 g per day of whole shiitake mushrooms can cause diarrhea, rashes and bloating.


Is This an Emergency?

If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911. If you think you may have COVID-19, use the CDC’s Coronavirus Self-Checker.