Skin lesion KOH exam
The 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
Your 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...
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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 under a microscope. The skin is tested to look for skin conditi...
Risks
There is a small risk of bleeding or infection from scraping the skin.
Reviewed By
Elika Hoss, MD, Assistant Professor of Dermatology, Mayo Clinic, Scottsdale, AZ. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
Babel DE. Fungal studies (and scabies): collection procedures and tests. In: Fowler GC, ed. Pfenninger and Fowler's Procedures for Primary Care. 4th ed. Philadelphia, PA: Elsevier; 2020:chap 17.
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.
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