Even Edible Shiitake Mushrooms Require Caution! A Guide to Preventing "Shiitake Dermatitis" and Mushroom Food Poisoning

1. What is "Shiitake Dermatitis" that can occur even with edible mushrooms?

Shiitake dermatitis is a skin disorder that occurs several hours to days after consuming raw or undercooked shiitake mushrooms, resulting in linear red rashes on the upper body and arms..

• Welt-like rashes that resemble scratches from a cat

• Intense itching

• Spreads to the torso, neck, and arms

These symptoms are typical, with a significant visual impact and intense itching being characteristic.

The cause is believed to be a type of "toxic dermatitis" that occurs when components in shiitake mushrooms enter the body in an undercooked state. It can occur even if allergy tests are negative, and there are not a few cases where people say, "I just cooked and ate them normally..."

2. When and how does it develop?

The timing of onset is generally as follows.

• It often appears 12 hours to 5 days after eating

• Cases where symptoms appear particularly 2 to 3 days later are noticeable

Since it does not appear immediately,it is difficult to notice the causal relationship with shiitake mushrooms, which is a troublesome point.

It's not only when you eat a large amount, but even a light amount like
a few grilled shiitake mushrooms
or a few slices in a hot pot
can cause it if undercooked.

3. Differences from mushroom food poisoning

There are broadly two types of mushroom food poisoning.

1. Food poisoning from poisonous mushrooms

   • The mushrooms themselves are toxic

   • Accidental consumption can lead to severe symptoms like vomiting, diarrhea, hallucinations, liver damage, or even death

   • It's extremely dangerous to decide "it's edible" based on amateur judgment
     
     

2. Troubles due to cooking or storage mistakes with edible mushrooms

   • Shiitake dermatitis, as well as gastrointestinal symptoms like abdominal pain and diarrhea

   • Triggered by raw, undercooked, or spoiled mushrooms

In other words,
"Do not eat poisonous mushrooms" and "Do not mishandle edible mushrooms"
are important to follow.

4. Symptoms that can occur with edible mushrooms

4-1. Shiitake Dermatitis

• Linear rashes on the torso and arms after consuming raw to undercooked shiitake

• Intense itching and welt-like appearance

• Most improve in a few days to a week, but seeing a doctor is recommended

4-2. Gastrointestinal Symptoms

• Abdominal pain, diarrhea, and nausea from undercooked or old mushrooms

• Symptoms similar to food poisoning from other ingredients

4-3. Food Allergies

• Some people have allergies to specific mushrooms like shiitake or enoki

• If you experience hives, swelling of lips or eyelids, or difficulty breathing, seek medical attention immediately

5. Basic rules for safely eating mushrooms

5-1. "Thoroughly cook to the center" is fundamental

Mushrooms are fungi, not vegetables, and raw or undercooked mushrooms may contain components that irritate the body.

• Cut thick shiitake mushrooms in half to make them easier to cook through

• Cook until the gills under the cap become tender and change color

• If it still looks hard or white, cook it a little longer

is reassuring.

5-2. Don't rely solely on the microwave

Microwaves can cause uneven heating, leaving the center undercooked.

• Stir once during microwave heating

• Finish by reheating in a frying pan or pot

, and using"microwave + stove"increases safety.

5-3. For storage, "use quickly" or "cook and freeze"

• Long-term storage in the refrigerator in a raw state leads to deterioration

• For unused portions, lightly boil or stir-fry and then freeze in portions

• Always cook frozen mushrooms before use

6. Safety points for shiitake in different cooking scenarios

6-1. Hot Pot Cooking

• Add shiitake early and boil thoroughly

• Wait until the cap shrinks significantly and the gills change color before eating

6-2. Foil Baking and Oven

• Open the foil and check the thick part of the cap with chopsticks to ensure it's soft inside

• If it's still hard, close the foil and extend the heating

6-3. Barbecue and Grilling

• Not just alongside meat,allocate a dedicated space for mushrooms to grill slowly

• Adjust the heat to medium to prevent the surface from burning while the inside remains raw

7. When to visit a medical facility

7-1. Gastrointestinal Symptoms

• Severe abdominal pain, repeated diarrhea or vomiting, fever

• Inability to retain fluids, lethargy, or bloody stools

If any of these occur,seek medical attention promptly.

7-2. When Shiitake Dermatitis is suspected

• Ate shiitake mushrooms several hours to days ago

• Subsequently developed numerous linear red welts on the upper body and arms

• Intense itching and spreading

In such cases,a visit to a dermatologist is recommended.

Noting "when, how much, and how the shiitake was cooked" can facilitate a smoother diagnosis.
※This article provides general information, and diagnosis and treatment should always follow a doctor's judgment.

8. Conclusion: Be aware and enjoy safely

• Shiitake dermatitis is a skin disorder triggered by raw to undercooked shiitake mushrooms

• It is a different issue from poisonous mushrooms, and it's important to know that "even edible mushrooms can cause poisoning if mishandled"

• The key points are

  1. Do not eat raw

  2. Thoroughly cook to the center

  3. Do not force yourself to eat spoiled mushrooms

  4. Seek medical attention promptly if you experience health issues or rashes

By following these four rules, mushrooms can be a reliable ally full of umami and dietary fiber.
This winter, enjoy "well-cooked mushroom dishes" like hot pots, sautés, and foil bakes with peace of mind.