Nail fungus (Onychomycosis) is a fungal infection of the toenail or finger nail. Nail fungus is most commonly found in toenails, due to the more damp and dark environment. As fungi can easily spread, nail fungus is very contagious. Additionally, nail fungus can involve all parts of the nail such as the nail plate, nail bed and nail root.
Nail fungus is typically caused by the fungi Dermatophytes, such as Trichophyton rubrum. However, other fungi and yeasts can also be responsible for nail fungus infections.