If every patient with interdigital maceration and fissuring were treated with a topical fungicide, only one third of them would improve. Accumulation of moist, hydrated keratin between the toes is usually interpreted simply as athlete's foot, but it develops from various unrelated causes. The gross appearances is similar regardless of cause, and yet, effective management depends entirely on accurate etiologic diagnosis.
The following conditions produce white maceration, erosion, and fissuring between the toes: (1) dermatophytosis, (2) candidiasis, (3) erythrasma, and (4) psoriasis.
Demonstration of hyphae on a direct potassium hydroxide mount and culture of one of the dermatophytic fungi (most commonly Trichophyton mentagrophytes) on Sabouraud's medium provides an accurate diagnosis of dermatophytosis ( Fig 1 ). The infection responds promptly to local application of an appropriate topical fungicide or systemic griseofulvin administration.
The pseudohyphae of Candida albicans can also be seen on direct microscopic examination, and the yeast grows rapidly on culture.
Kingery FAJ. Imitators of Athlete's Foot. JAMA. 1965;193(11):953. doi:10.1001/jama.1965.03090110091022