In most cases, your health professional can diagnose athlete's foot (tinea pedis) by looking at your foot. He or she will also ask about your symptoms and any previous fungal infections you have had.

If your symptoms look unusual or if a previous infection has not responded well to treatment, your health professional 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.