Fungal nails usually affect your toe nails, but can sometimes affect the nails on your hands. It is a common condition that usually begins with a white or yellow spot under your fingernail or toenail. As the fungal infection spreads, it usually thickens, discolours and crumbles your nails. It can spread to other nails and cause discomfort. Our podiatrist can offer various treatment options for fungal nails.