Onychomycosis is a fungal infection of the nail. It is the most common disease of the nails and accounts for about half of all nail abnormalities. This condition may affect toenails or fingernails, but toenail infections are particularly common. It occurs in about 10% of the adult population. The risk of infection increases with age with about 48% of those older than 70 suffering from it.
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, the skin can become inflamed and painful underneath and around the nail. Fungi from the nails may precipitate secondary bacterial infections, cellulitis and chronic urticaria. Infected toenails can also act as a reservoir for fungi, allowing the transmission to other areas of the body or even other people.
There is usually no pain or other physical symptoms, unless the disease is severe. People with onychomycosis may experience significant psychosocial problems due to the appearance of the nail, particularly when fingers – which are always visible – rather than toenails are affected.
Certain conditions make it more likely to suffer from nail fungi. These include diabetes, poor peripheral circulation, a predisposition towards sweating and generally old age.