Skin lesion KOH exam

Potassium hydroxide examination of skin lesion

The health care provider scrapes the problem area of your skin, using a blunt edge, such as the edge of a microscope slide. The scrapings from the skin are placed in liquid containing the chemical potassium hydroxide (KOH). The liquid is examined under the microscope. KOH destroys all non-fungal cells. This makes it easier to see if there is any fungus present.

There is no special preparation for the test.

You may feel pressure or pain when the provider scrapes your skin.

This test is done to diagnose a fungal infection of the skin.

No fungus is present.

Fungus is present. The fungus may be related to ringworm, athlete's foot, jock itch, or another fungal infection.

There is a small risk of bleeding or infection from scraping the skin.