Dermatophytid (identity or id) reactions are protean; they are not related to localized growth of the fungus but rather are an inflammatory reaction to a dermatophytosis Overview of Dermatophytoses Dermatophytoses are fungal infections of keratin in the skin and nails (nail infection is called tinea unguium or onychomycosis). Symptoms and signs vary by site of infection. Diagnosis is by... read more elsewhere on the body. Lesions are typically pruritic but may manifest as
Vesicular eruptions on the hands and feet
Erythema annulare centrifugum
Distribution may be extensive.
Diagnosis of dermatophytid reaction is by potassium hydroxide wet mounts that are negative at the site of the id reaction and positive at the distant site of dermatophyte infection.
Treatment of the primary infection cures dermatophytid; pending cure, topical corticosteroids and/or antipruritics (eg, hydroxyzine 25 mg orally 4 times a day) can be used to relieve symptoms (see Table: Options for Treatment of Superficial Fungal Infections* Options for Treatment of Superficial Fungal Infections* ).