Also called onychomycosis, nail fungus is far more common than many might think. It starts as a small white or yellowish spot under a nail, and it may go unnoticed and never become a problem. When it does, however, it can affect several nails and cause unsightly thickening and crumbling of the nails.
Nail fungus can affect fingernails, but it is more often a problem affecting toenails. Symptoms include a thickening of the nail, accompanied by yellow and brownish discoloration of the nail. Nails may become brittle and distorted, and may become ragged or crumble at the ends. You may also experience pain or odor with a more extensive infection.
Multiple types of fungi can cause this condition, but, while it may spread to multiple nails, it is extremely unusual to become infected from someone else. This type of infection is more prevalent among people who sweat heavily or who have a history of athlete’s foot, which also is caused by fungi. It also is more common among older people, as older nails become brittle and crack, allowing a path for fungi to get underneath a nail. Poor circulation, psoriasis, diabetes or a weakened immune system also can make you more susceptible to a fungal infection of the toenails.
Severe fungal infections should be checked by a doctor, especially if you have diabetes or have recently experienced an injury to your feet or toes.