Koh preparations (potassium hydroxide) & bull; hello healthy

Definition

What is a koh (potassium hydroxide) preparation?

KOH (potassium hydroxide) preparations are useful for finding out if there is a fungal infection on the skin. The doctor obtains tissue samples using a scalpel or other instrument. Heat and KOH are then used in the sample to dissolve keratin — the protein fiber that is the main component of nails — and the skin cells that make keratin. After these substances have been removed, fungal elements can be detected under a microscope.

When do I need a potassium hydroxide preparation test?

If you have itchy, red, or scaly skin with visible bumps on the edges, a KOH test may be done to find if you have a skin yeast infection.

Precautions & warnings

What should I know before undergoing a koh (potassium hydroxide) preparation?

Your doctor may be able to tell if you have a yeast infection by the appearance of a rash and may not need to do a KOH test. If the sample is too small or is taken from an area that is not infected with the fungus, a false negative result may be obtained. Previous use of antifungal drugs may also give false negative results.

Process

What should I do before taking the koh (potassium hydroxide) preparation?

No special preparation is required for this test.

How is the potassium hydroxide preparation test process?

A skin sample is taken by lightly scratching the infected area. If the skin is the site where infection is suspected, the doctor will scratch the abnormal outer layer of skin with a scalpel. If the scalp is affected, the doctor will gently remove the affected hair with forceps and also scratch the scalp with a scalpel. For nail infections, the examiner scrapes the inner surface of the nail under the tip or cuts a part of the nail that looks abnormal.

What should I do after the potassium hydroxide preparation test?

You may experience some discomfort while the sample is being collected. Sample collection takes about 1 minute, and results usually take effect within 10 minutes. You can return to your normal activities when you finish the test. The doctor will discuss with you about the condition and provide the appropriate treatment. Sometimes, the doctor may order further tests. Follow the doctor's instructions carefully.

Explanation of the Test Results

What do my test results mean?

Normal

There was no fungus in the skin sample. If the result is negative, the doctor may take a second sample or order a sample of fungal cells.

Abnormal

There is fungus in the skin sample. If fungal organisms are detected under a microscope, the doctor will prescribe an appropriate antifungal drug. In some cases, it may be done to collect fungal cells to confirm results or identify specific types of fungi.