A KOH prep test is a simple, non-invasive procedure for diagnosing fungal infections of the

skin or nails. Cells are obtained from the affected area, placed on a slide with a solution

consisting of potassium hydroxide, and examined under a microscope to look for signs of a

fungus.1 Also called a potassium hydroxide skin lesion exam, fungal smear, or skin scraping,

the KOH prep test is quick, accurate, and virtually painless.