Toenail fungus is a fungal infection which may affect one or more of the nails. An infection with nail fungus may begin as a white or yellow spot under the tip of a fingernail or toenail. As the nail fungus spreads deeper into the nail, it may cause nail to discolor, thicken and develop crumbling. Toenail fungus treatment Los Angeles can treat this unsightly and potentially painful problem very effectively.