Fungal skin infection. Inflamed skin (erythema) on the neck of a patient infected with the fungus Trichophyton mentagrophytes. This dermatophyte ringworm fungus can cause beard ringworm (tinea barbae), athlete's foot (tinea pedis) and scalp ringworm (tinea capitus). It is one of many fungi that can grow in human skin, causing inflammation and itching. Ringworm is treated with antifungal drugs.