A 49-year-old Hispanic woman presented with a 4-month history of scaling and a macerated rash localized between her toes (FIGURE 1). The rash was malodorous, mildly erythematous, and sometimes associated with pruritus. The patient had no relevant medical history. Potassium hydroxide (KOH) testing was performed and found to be negative. So a Wood’s lamp was used to examine the patient’s toes—and it revealed the diagnosis.