Skin lesion KOH exam
Potassium hydroxide examination of skin lesionThe skin lesion KOH exam is a test to diagnose a fungal infection of the skin.
Fungal infection of the skin
Candida infection of the skin is a yeast infection of the skin. The medical name of the condition is cutaneous candidiasis.
How the Test is Performed
The health care provider scrapes the problem area of your skin using a needle or scalpel blade. The scrapings from the skin are placed on a microscope slide. Liquid containing the chemical potassium hydroxide (KOH) is added. The slide is then examined under the microscope. KOH helps dissolve much of the cellular material. This makes it easier to see if there is any fungus.
Potassium hydroxide
Potassium hydroxide is a chemical that comes as a powder, flakes, or pellets. It is commonly known as lye or potash. Potassium hydroxide is a caust...
Read Article Now Book Mark ArticleHow to Prepare for the Test
There is no special preparation for the test.
How the Test will Feel
You may feel a scratching sensation when the provider scrapes your skin.
Why the Test is Performed
This test is done to diagnose a fungal infection of the skin.
Normal Results
No fungus is present.
What Abnormal Results Mean
Fungus is present. The fungus may be related to ringworm, athlete's foot, jock itch, or another fungal infection.
Ringworm
Ringworm is a skin infection due to a fungus. Often, there are several patches of ringworm on the skin at once. The medical name for ringworm is ti...
Athlete's foot
Athlete's foot is an infection of the feet caused by fungus. The medical term is tinea pedis, or ringworm of the foot.
Jock itch
Jock itch is an infection of the groin area caused by a fungus. The medical term is tinea cruris, or ringworm of the groin.
If the results are uncertain, a skin biopsy may need to be done.
Skin biopsy
A skin lesion biopsy is when a small amount of skin is removed so it can be examined. The skin is tested to look for skin conditions or diseases. A...
Risks
There is a small risk of bleeding or infection from scraping the skin.
References
Chernecky CC, Berger BJ. Potassium hydroxide preparation (KOH wet mount) - specimen. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier Saunders; 2013:898-899.
Fitzpatrick JE, High WA, Kyle WL. Diagnostic techniques. In: Fitzpatrick JE, High WA, Kyle WL, eds. Urgent Care Dermatology: Symptom-Based Diagnosis. Philadelphia, PA: Elsevier; 2018:chap 2.
Tinea (ringworm) - illustration
Ringworm is a common skin disorder, especially among children, but may occur in people of all ages. It is caused by mold-like fungi (dermatophytes).
Tinea (ringworm)
illustration
Review Date: 4/16/2019
Reviewed By: Michael Lehrer, MD, Clinical Associate Professor, Department of Dermatology, University of Pennsylvania Medical Center, Philadelphia, PA. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
