Fungi are constantly around us in the environment and on our skin. Infections usually develop when something makes the nails particularly vulnerable and the fungus more able to grow - for example, when your feet or hands are constantly hot and moist. A similar fungus to the one which causes athletes foot, which is often called tinea, causes most infections. But other fungi can also cause problems. For example, Candida, which is a yeast, can cause a nasty infection of the skin fold around the edge of the nail.
Nails infected by fungi can look very unpleasant.
They may change colour, becoming white, yellow, green - or even black. Growth is distorted and the nail may be thickened or crumbly. In order to get the right treatment it's very important that the exact cause of the infection is pinned down. This can be done by taking clippings or scrapings from the nail and sending them off to the laboratory. Fungal infections of the nails won't get better on their own, and can take many weeks to treat because it is difficult to get to the fungus buried in the thick, hard nail.