When fungi incade a nail, they usually start at its free edge, and then spread down the side of the nail towards its base. Eventually the whole nail may beinvolved. The infected areas turn white or yellowish, and become thickened and crumbly. Less common patterns of infection include white patches or streaks on the nail surface. The nails most commonly affected by fungal infections arethose on the big and little toes. When several fingernails are infected, they are usually on the same hand.