Here's the main thing you need to know about nail fungus: AVOID. Seriously, the best way to treat this stubborn condition is to prevent it in the first place. I've compiled a few suggestions on how to do just that, plus some treatment options if you wind up with an infection.
What it is: Nail fungus is an infection of the nail bed. It often begins as a white or yellow spot under the nail, then spreads to the entire nail. Full-blown fungus usually makes the nail thick, brittle, and yellowed, with crumbly edges to the nail. (You can see pictures if you like, but you've been warned: it ain't pretty.)
How it's transferred: Fungi thrive in warm, dark, damp places, then happily transfer to your toenails or fingernails.
How to avoid it: Never walk barefoot in a public place such as a shower or swimming pool; instead, wear flip-flops to protect your feet from potential fungus hangouts. If you've battled nail fungus before, wear shoes and socks that "breathe," rather than nylons or socks that trap moisture. Take your own tools to nail salons, and never use the Jacuzzi-type foot-soaking tubs — they're harder to sanitize, so you risk picking up someone else's fungus.
To find out how to treat nail fungus, read more.
If you already have nail fungus, you have my condolences. This is one stubborn infection, and it won't go away on its own. In fact, left untreated, the fungus will grow and grow, and it may spread to other nails. While it won't kill you, it's smart to tackle it rather than ignore it.
The best bet is to see a doctor, who may prescribe an antifungal medicine such as Lamisil. (See the little guy up there? He's their fungal spokesperson.) This type of medicine helps new nails grow without fungus, but it takes months to grow a new nail. You may also need to have tests to make sure your liver stays healthy while you take the medicine. Worse yet, these medications can run into the hundreds, if not thousands, of dollars.
Over-the-counter treatments are more or less worthless. Any drugstore will have topical anti-fungal products, but read the label; most, if not all, treat the skin around the nail, but not the nail itself. Folk remedies include using tea tree oil on the nail every night, but that's a hit-or-miss plan. Some people swear by using Vicks Vapo-Rub on the nail; while I haven't had nail fungus, the hypochondriac in me thought I did, and I wore Vapo-Rub to bed for two weeks. (Sexy.) It turned out that my fungus fears were for nothing, but the Vicks treatment did improve some of the discoloration left over from wearing red polish.
As you can see, battling nail fungus is not easy. Once again, it all goes back to prevention. If you can avoid picking it up, please do.