Nail fungal infections occur under the fingernail or toenail as a result of exposure to a warm, moist environment like sweaty shoes or shower floors. These fungal infections usually begin as a yellow or white spot under the nail, and develop into thickened, brittle and distorted nails. They may also turn your nails a darker color as a result of the debris building up. Nail fungal infections occur more frequently in toenails because they are more often confined to dark, moist environments.
Nail fungal infections should be treated immediately as they may cause permanent damage and are likely to recur. Treatment options include oral anti-fungal medications, anti-fungal nail polish or other topical medications. The nail may need to be removed in severe infections.