What are the physical findings of dermatophyte id reactions in tinea capitis (scalp ringworm)?

Updated: Feb 21, 2020
  • Author: Marc Zachary Handler, MD; Chief Editor: Dirk M Elston, MD  more...
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Answer

Dermatophyte idiosyncratic or id reactions are manifestations of the immune response to dermatophytosis. Id reactions occur at a distant site, and the lesions are devoid of organisms. Id reactions may be triggered by antifungal treatment.

The most common type of id reaction is an acute vesicular dermatitis of the hands and feet. The grouped vesicles are tense, pruritic, and sometimes painful. Id reactions are noted in patients with inflammatory ringworm of the feet, primarily resulting from infection by Trichophyton mentagrophytes. Similar lesions may occur on the trunk in tinea capitis. Vesicular lesions may evolve into a scaly eczematoid reaction or a follicular papulovesicular eruption.

Other less common types of id reactions include annular erythema and erythema nodosum. These patients have a strong delayed-type hypersensitivity reaction to intradermal trichophytin.


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