Toenail fungus (onychomycosis) is caused by a group of fungi known as dermophytes. This group thrives on skin and on keratin, the main component of hair and nails. The fungus gets under the nail and begins to grow, damaging the nail so it discolors, becoming white, brown or yellow. Eventually, the nail might thicken, harden, become brittle and even fall off.
Your physician may perform a simple test called a potassium hydroxide (KOH) preparation for microscopic fungal examination in the office or laboratory. This test can be used to confirm the presence of a fungal infection. This test is performed by using a microscope to examine small flakes of skin from the rash. Many dermatologists perform this test in their office with results available within minutes. Rarely, a small piece of skin may be removed and sent for biopsy or fungal culture to help confirm the diagnosis.
What you need to know about fungal infections Some fungi occur naturally in the body, and they can be helpful or harmful. An infection occurs when an invasive fungus becomes too much for the immune system to handle. We describe the most common types, including yeast infection, jock itch, and ringworm. Here, learn about risk factors and the range of treatments. Read now
If you have diabetes, you may have reduced blood circulation and nerve supply in your feet. You're also at greater risk of a bacterial skin infection (cellulitis). So any relatively minor injury to your feet — including a nail fungal infection — can lead to a more serious complication. See your doctor if you have diabetes and think you're developing nail fungus.