I can tell you my own mother struggled with toenail fungus on her big toe for over 10 years, and the reason why she originally got it and then continued to struggle with this fungus was the chemotherapy she went through when diagnosed with breast cancer years ago. After going through chemo, she had systemic yeast and candida issues and then developed the toenail fungus. The exact treatment I detail below is what we used with her to successfully erase her fungus.
Infected nails are usually thicker than normal and could be warped or oddly shaped. They can break easily. Nails with fungus might look yellow. Sometimes a white dot shows up on the nail and then gets bigger. When fungus builds up under your nail, it can loosen and even separate the nail from the bed. The fungus can also spread to the skin around your nail.