What causes toe nail fungus?

Skin fungi: The same dermatophytic fungi that cause athlete's foot and jock itch.

See a podiatrist: Fungus is everywhere. The nail plate typically is smooth and adhered to the underlying bed, but if there is any damage that causes the nail plate to lift and/or there is a change in the texture of the nail plate, fungus is very opportunistic. The key for treatment is prevention and getting rid of environments that fungus like. A podiatrist can recommend topical, oral or even laser therapy.