In a horse with severe sweet itch and a history of corticosteroid treatment for this disorder, a single, well-circumscribed and crusty white lesion was present on the thigh. The geophilic dermatophyte species M. gypseum was cultured from the lesion. The lesion was treated topically once a week with an enilconazole emulsion for four weeks. Full recovery was noted after two months. This case suggests that sweet itch combined with systemic corticosteroid treatment, may act as predisposing factor for dermatophyte infection. In addition, the importance of correct isolation and identification of the causal agent is highlighted.