Fungus infections of the nails, the great toe, can be caused by a number of different pathogens. One of the most uncommon (get ready for the big words) is a nondermatophyte mold. We won’t go into the name of the three most common molds, it isn’t necessary to know.
Toenail Fungus

Dermatophytes or the organisms that cause nail fungus infections are abundantly found in the floor of commercial areas as for example public bathing places like by the side of swimming pool etc. Research studies have shown that there could be about 100 fungal fragments/m2 plus minute pieces of keratin in these areas. In those areas with staircases the figure could be greater than 700 fungal fragments/m2 of floor space. Any one of these fragments could cause infection. This probably explains why there are more fungal infections like nail fungus infection.
Toenail Fungus

The reason why nail fungus is difficult to treat is because it could reoccur despite being rid of the problem earlier. Another reason is it takes up to a year for a new toe nail to grow. This makes both treatment and cure difficult.
Toenail Fungus

Nail fungus is the commonest disease of the nail. But it should not be confused with other nail disorders.

For example, it should not be confused with athlete’s foot. Athlete’s foot occurs in the skin of the foot and sometimes it is possible that nail fungus and athlete’s foot could occur concurrently.
Nail fungus should not be mistaken for bacterial infections caused by Pseudomonas aeruginosa which could make the nail black or green in color. Only a doctor can confirm whether you indeed have nail fungus infection.
In the elderly the nail could thicken and scale beneath the nail. This is not caused due to fungus but is due to peripheral vascular disorders.
Nail fungus should not be confused with psoriasis of the nail and other conditions like onycholysis wherein the nail plate separates from the underlying structure.
Toenail Fungus