KOH (potassium hydroxide) preparation test for athlete's foot
Examination Overview
The KOH preparation test is used to determine whether there is a fungal infection of the skin, such as athlete's foot.
Your health professional will take samples by lightly scraping the skin of your foot with a sharp blade or the edge of a microscope slide. He or she may also take nail samples if a toenail is also infected. The skin or nail scrapings are placed on a slide with potassium hydroxide (KOH) solution and heated. This solution dissolves the skin cells but not the fungus cells. The fungus cells can then be seen with a microscope. Colour stains can be used to highlight the fungi.
Why It Is Done
A KOH preparation may be done to determine the cause of cracking, scaling, peeling, or blistered skin, or if there is an area of persistent irritation (and sometimes redness) on the feet. The presence of fungi suggests that the condition is probably athlete's foot.
Results
Normal
No fungi are present in the skin or nail scrapings. Other skin tests may be done to determine the cause of the skin inflammation or nail problems.
Abnormal
Fungi are present in the skin or nail sample.
What To Think About
Test results on severe toe web
infections may not always show fungi. In this case, a bacterial infection may hide the fungal infection.
If you have been diagnosed with athlete's foot before and the symptoms have returned, a KOH preparation test will probably not be necessary. Your health professional may suggest you treat the infection with non-prescription or prescription antifungal medication.
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| Author: | Douglas Dana Amy Fackler, MA Debby Golonka, MPH | Last Updated: September 7, 2006 |
| Medical Review: | Patrice Burgess, MD - Family Medicine Tom Bailey, MD - Family Medicine Randall D. Burr, MD - Dermatology | |
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| Topic Contents | |
| Examination Overview | |
| Why It Is Done | |
| Results | |
| What To Think About | |