Toenail fungus infection is a very contagious. This kind of infection can be very embarrassing issue and sometimes it can also be very painful. These fungus infection used to develop when fungi, which is generally known as dermatophytes, and burrow under the toenails that causes then to become discolored, crusty, distorted and thick as well. In other terms, toenail fungus infection is also known as onychomycosis.