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 Values What abnormal results mean What the risks are Special considerations

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 lesion is scraped, using a blunt edge such as the edge of a microscope slide. The scrapings from the skin lesion are placed in a solution of potassium hydroxide (KOH) and examined under the microscope. The fungus can be seen, if present. This is different from a saline (salt water) examination, since the KOH destroys all non-fungal cells, making it much easier to see the fungal material.

How to prepare for the test Return to top

There is no special preparation for the test.

Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

Infant test or procedure preparation (birth to 1 year)
Toddler test or procedure preparation (1 to 3 years)
Preschooler test or procedure preparation (3 to 6 years)
Schoolage test or procedure preparation (6 to 12 years)
Adolescent test or procedure preparation (12 to 18 years)

How the test will feel Return to top

You may feel a pressure sensation when the lesion is scraped from the skin.

Why the test is performed Return to top

The test is performed when fungal infections of the skin are suspected.

Normal Values Return to top

The lack of fungus is normal and expected.

What abnormal results mean Return to top

The KOH smear shows hyphae or fungal organisms. This may indicate ringworm (tinea corporis), athlete's foot, jock itch, or many other fungal infections.

What the risks are Return to top

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

Special considerations Return to top

Not applicable.

Update Date: 10/27/2003

Updated by: Jeffrey Drayer, M.D., Dermatologist, Los Angeles, CA. Review provided by VeriMed Healthcare Network.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.