How common is toenail fungus?

Fungal toenails are fairly common, but they can go undetected for years because the initial symptoms are so subtle. The problem, known medically as onychomycosis, develops when a fungus infects the area under the surface of a toenail. There are many types of fungal infections, which are believed to affect 3% to 5% of people in the United States at any given time. Only about one in four of these people seeks help. Podiatrists, however, think these estimates are far too low, and that the percentage affected is even higher. A recent study that tracked the most common skin and nail fungal infections around the globe found that in the past several decades, these infections have increased steadily, and now affect more than 20% to 25% of the world's population.