Fungal nails are not usually serious, but can be unpleasant and difficult to treat. Most fungal nail infections occur as a result of the same fungi that causes athlete’s foot. The infection starts from the furthest end of the toe and develops along the nail bed towards the cuticle. The infection develops slowly and causes the nail to become discoloured, thickened and distorted. Although not all thickened and distorted nails are caused by a fungal infection.