MedlinePlus Medical Encyclopedia: Skin lesion KOH exam

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Skin lesion KOH exam

Contents of this page:
Illustrations Alternative Names Definition How the Test is Performed How to Prepare for the Test	How the Test Will Feel Why the Test is Performed Normal Results What Abnormal Results Mean Risks

Illustrations

Viral lesion culture

Alternative Names Return to top

Potassium hydroxide examination of skin lesion; Fungal wet prep

Definition Return to top

The skin lesion KOH exam is a test to diagnose a fungal infection of the skin.

How the Test is Performed Return to top

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

How to Prepare for the Test Return to top

There is no special preparation for the test.

How the Test Will Feel Return to top

You may feel pressure when the doctor scrapes the lesion off your skin.

Why the Test is Performed Return to top

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

Normal Results Return to top

Normally, there is no fungus.

What Abnormal Results Mean Return to top

The KOH smear shows fungus, which may be related to ringworm, athlete's foot, jock itch, or another fungal infection.

Risks Return to top

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

Update Date: 4/16/2007

Updated by: Michael S. Lehrer, M.D., Department of Dermatology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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