What are the other Names for this Condition? (Also known as/Synonyms)

• Flagellate Mushroom Dermatitis
• Lentinula Edodes Dermatitis
• Shiitake Mushroom-Induced Flagellate Erythema

What is Shiitake Dermatitis? (Definition/Background Information)

• Shiitake Dermatitis is a skin disorder that occurs on consuming undercooked shiitake mushrooms. It results in the formation of red, itchy skin papules in different areas of the body
• The shiitake is an edible mushroom that was mostly cultivated in parts of East Asia (chiefly China and Japan). However, now, this species forms nearly a fourth of yearly global mushroom production and is popular across the world
• On consumption of raw or poorly-cooked shiitake mushrooms, it leads to a toxic reaction in the body, owing to certain chemical compounds contained in the mushroom. Shiitake Mushroom Dermatitis predominantly results in skin rashes. Individuals do not usually have any other signs and symptoms, although occasionally fever, malaise, body ache, and diarrhea may be noted
• In a majority of individuals, no treatment is needed for Shiitake Dermatitis since it resolves on its own within about 10-21 days. However, if required, topical creams and antihistamine medications may be prescribed by the healthcare provider
• Shiitake Dermatitis is a self-limiting condition, and hence, the prognosis of the condition is excellent in most cases. The condition may be prevented by properly cooking the shiitake mushrooms prior to consumption

Who gets Shiitake Dermatitis? (Age and Sex Distribution)

• Shiitake Dermatitis may affect individuals of any age
• It can affect both males and females
• The condition can occur worldwide; individuals of all racial and ethnic background may be affected. However, higher incidences are seen among certain Asian populations

What are the Risk Factors for Shiitake Dermatitis? (Predisposing Factors)

• The primary risk factor for Shiitake Dermatitis is eating uncooked or poorly-cooked shiitake mushrooms
• Being in countries, where the consumption of shiitake is more common, such as in China and Japan

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Shiitake Dermatitis? (Etiology)

The exact mechanism of Shiitake Mushroom Dermatitis development is unknown. It develops on consuming raw or improperly cooked shiitake (Lentinula edodes) mushrooms. Shiitake Dermatitis is considered to be a toxic reaction to certain chemical compounds present in the mushroom.

• Scientific research has suggested that certain polysaccharides present in shiitake mushrooms may be the cause of the skin rashes. Hence, the condition is described as being toxin-induced
• The polysaccharide compound is called ‘lentinan’, which decomposes upon exposure to heat. Adequately cooking the mushroom can help neutralize the compound and prevent the whiplash-like skin rashes from developing
• Occasionally, Shiitake Dermatitis can occur after consuming shiitake mushrooms with subsequent exposure to sun. This results in the formation of rashes on sun-exposed areas of the body. This condition is termed photosensitive Shiitake Dermatitis

It is important to note that not all individuals who consume uncooked or poorly-cooked shiitake mushrooms manifest the skin symptoms.

What are the Signs and Symptoms of Shiitake Dermatitis?

The signs and symptoms of Shiitake Dermatitis may be mild or severe. It may also vary from one individual to another. In general, the signs and symptoms include:

• Presence of erythematous (red) skin papules in several areas of the body; the rashes appear in a linear and curvilinear pattern (flagellate erythema)
• The rashes are very itchy and can lead to scratching
• Scratching results in flagellate dermatitis, wherein groups of linear papules form along the line of scratching
• Scratching and/or rubbing the area may also make the condition worse, resulting in bleeding
• Almost all individuals show rashes on the back and chest (trunk), and a majority presents them on the arms and legs, face, and neck region, etc.
• Hyperpigmentation, or increased pigmentation, of the skin is not observed
• Absence of fever
• The onset of Shiitake Dermatitis is within 2-3 days of raw/uncooked mushroom consumption

Involvement of other body systems, such as the digestive, neurological, respiratory, systems, or involvement of the mucus membranes are generally absent.

How is Shiitake Dermatitis Diagnosed?

The following are the diagnostic methods that may be used for Shiitake Dermatitis:

• A thorough physical examination and a complete medical history are very crucial. A diagnosis of Shiitake Dermatitis includes analyzing the classical signs and symptoms of the condition and history of consumption of shiitake mushrooms
• Blood tests, such as complete blood count, and urine tests, as required may be undertaken
• Dermoscopy: Dermoscopy is a diagnostic tool where a dermatologist examines the skin using a special magnified lens
• Wood’s lamp examination: In this procedure, the healthcare provider examines the skin using ultraviolet light. It is performed to examine the change in skin pigmentation
• Culture studies may be performed to rule out any infections
• Skin biopsy: A skin tissue biopsy is performed and sent to a laboratory for a pathological examination. The pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis

Note: In most cases, a tissue biopsy is not needed to diagnose Shiitake Dermatitis.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Shiitake Dermatitis?

No significant complications due to Shiitake Dermatitis have been reported. If the condition is severe, then the following complications may be observed:

• Cosmetic issues that result in emotional stress
• Bleeding and ulceration of the skin may result in secondary viral or bacterial infections
• Recurrence of the skin rashes on consumption of uncooked shiitake mushrooms again

How is Shiitake Dermatitis Treated?

Generally, there is no treatment required for Shiitake Dermatitis since it is self-resolving. If the skin symptoms are severe, then symptomatic treatment measures may be instituted. These may include:

• Administration of oral antihistamines medications
• Application of topical corticosteroids
• During the healing process, it is best to avoid sun exposure

A few self-care tips and home remedies for Shiitake Dermatitis may include:

• Completely avoid scratching the affected areas
• A comfortable and cool bath may help soothe the skin; but, avoid excessive washing and scrubbing of the skin
• Wear smooth cotton clothes
• Use only mild perfumes, soaps, and detergents

Taking care of oneself, being clean and hygienic (especially face and hands), avoiding the urge to touch/break the blisters, avoiding oily make-ups and creams, drinking lots of water, etc. are all simple practices that can ensure a faster recovery from the condition.

How can Shiitake Dermatitis be Prevented?

Shiitake Dermatitis may be prevented through the following measures:

• Avoid the consumption of raw shiitake mushrooms, such as in salads
• Avoid tasting the mushrooms while they are being cooked
• Providing warning or advisory labels on shiitake mushroom packets that are sold in shops and supermarkets
• Thoroughly cooking the mushrooms to a temperature of 145 deg. Celsius or more, decomposes the chemical compound causing the skin condition. This helps eliminate the risk of Shiitake Dermatitis

It is important to recognize and be aware of Shiitake Dermatitis since these mushrooms are consumed worldwide.

What is the Prognosis of Shiitake Dermatitis? (Outcomes/Resolutions)

• The prognosis of Shiitake Dermatitis is generally excellent since it is a self-limited condition. There are no serious complications observed with the condition
• The skin rashes are known to completely disappear within about 2 to 3 weeks following its onset

Additional and Relevant Useful Information for Shiitake Dermatitis:

• Cleaning the skin too hard with strong chemicals or soaps may aggravate the skin condition. Care must be taken avoid strong soaps and chemicals that could potentially worsen the condition
• The presence of dirt on the body is not a causative factor for Shiitake Dermatitis. However, it helps to be clean and hygienic, which will help the condition from getting worse