Skin lesion KOH exam - All Information

Alternative Names

Potassium hydroxide examination of skin lesion

Definition of Skin lesion KOH exam:

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

How the test is 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.

How to prepare for the test:

There is no special preparation for the test.

How the test will feel:

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

Why the test is performed:

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

Normal Values:

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.

What the risks are:

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

Viral lesion culture

Reviewed last on: 5/13/2011
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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