A fungal nail infection occurs when a fungus attacks a fingernail, a toenail, or the skin under the nail, called the nail bed. Fungi (plural of fungus) can attack your nails through small cuts in the skin around your nail or through the opening between your nail and nail bed.
If you are healthy, a fungal nail infection probably won't cause serious problems. But it may look bad, hurt, or damage your nail or nail bed.
A fungal nail infection could lead to more serious problems if you have diabetes or a weak immune system. Talk to your doctor about the best way to treat a nail infection if you have one of these problems. Read more about the causes, symptoms, and treatments for fungal nail infections.