Onychomycosis – is a fungal infection of the nail. It is another one of the most common diseases of the nails and constitutes about half of all nail abnormalities. This condition may affect toenails or fingernails, but toenail infections are particularly common. It occurs in about 10 percent of the adult population. The most common symptom of a fungal nail infection is the nail becoming thickened and discoloured: white, black, yellow or green. As the infection progresses the nail can become brittle, with pieces breaking off or coming away from the toe or finger completely. If left untreated, this condition can spread from toe to toe until both feet and hands are affected. In approximately half of suspected nail fungus cases there is no fungal infection, but only nail deformity. A confirmation of fungal infection should precede treatment. Avoiding use of oral antifungal therapy in persons without a confirmed infection is a particular concern because of the side effects of that treatment, and because persons without an infection should not have this therapy.