Currently, a mycid is defined as hyperergic reaction that develops from a remote localized infection and in which no fungus is detectable. Criteria for a mycid caused by a dermatophyte (dermatophytid) are (1) proven dermatophytosis elsewhere, (2) no evidence for fungal elements in the lesions of the -id reaction, (3) initially often worsening of the lesions under therapy with highly potent systemic antimycotics, and (4) clearing after the dermatophytosis has been treated sufficiently. The most common dermatophytid is a symmetrical dyshidrotic mycid of the hands in connection with an often highly inflammatory mycotic infection of the feet especially by Trichophyton mentagrophytes. In addition to lichen trichophyticus, dermatophytids associated with tinea capitis may show high clinical variability. They often occur under systemic antimycotic therapy and have to be differentiated from drug reactions. In addition to systemic antimycotic therapy and, if necessary, a short-term application of oral glucocorticoidsteroids, a topical combination of an antifungal and a glucocorticosteroid is effective. It leads to an immediate reduction of inflammation and pruritus, especially if initiation of systemic antifungal therapy has resulted in a flare-up reaction (overtreatment phenomenon).