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DOI:
https://doi.org/10.57187/5389

Clinical reasoning: Case report

Vol. 156 No. 7 (2026)

Whip-like rash in the emergency room: shiitake-induced flagellate dermatitis, a case report

Cite this as:
Swiss Med Wkly. 2026;156:5389
Published
16.07.2026

Summary

Shiitake-induced flagellate dermatitis is a rare cutaneous reaction characterised by linear, erythematous, itchy lesions that appear after the consumption of raw or undercooked shiitake mushrooms. Shiitake mushrooms are traditionally consumed in Asian countries such as Japan, where the first case of flagellate dermatitis was documented. As shiitake mushrooms have become increasingly popular in Western countries, the incidence of this reaction has increased.

We present the case of a 54-year-old man who presented to the emergency room with widespread linear erythematous skin lesions and was diagnosed with shiitake-induced flagellate dermatitis, a condition that is rarely reported in Western emergency settings. The case was triggered by undercooked rather than raw shiitake mushrooms.

The dermatologist’s pattern recognition skills and detailed enquiry into the patient's dietary history enabled the diagnosis. His symptoms resolved completely within one week following treatment with oral antihistamines and topical corticosteroids.

When considering the differential diagnosis of flagellate dermatitis, clinicians should include adverse drug reactions, particularly those related to chemotherapeutic agents, as well as systemic diseases such as dermatomyositis, adult-onset Still’s disease, systemic-onset juvenile idiopathic arthritis, and, less commonly, phytophotodermatitis or infectious exanthems. In cases presenting with atypical linear skin eruptions, clinicians should also inquire about the patient’s dietary history.

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