If your symptoms look unusual or if a previous infection has not responded well to treatment, your doctor may collect a skin or nail sample by lightly scratching the skin with a blade or the edge of a microscope slide, or by trimming a nail. He or she will examine the skin and nail samples using laboratory tests including:
- KOH (potassium hydroxide) preparation, to confirm the presence of fungi.
- Fungal culture, to identify the type of fungus present.
In rare cases, a skin biopsy will be done by removing a small piece of skin that will be looked at under a microscope.