Skin lesion KOH exam

Alternative Names: Potassium hydroxide examination of skin lesion

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

Why is the Test Performed?

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

How is the Test Performed?

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.

Preparation for the Test

There is no special preparation for the test.

How will the Test Feel?

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

Skin lesion KOH exam Risks

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

Normal Results for Skin lesion KOH exam

Normally, there is no fungus.

What Abnormal Results Mean

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

Viral lesion culture

Review Date: 5/13/2011
Reviewed By: Kevin Berman, MD, PhD, Atlanta Center for Dermatologic Disease, Atlanta, GA. Review provided by VeriMed Healthcare Network.  Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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