A yellowish toenail is typically a sign of fungus, which thrives in moist environments such as public pools, showers, and shoes. When it invades the nail, the fungus can cause an infection called Onychomycosis. The infection usually starts at one corner of the nail and spreads toward the cuticle. The first (`big") and last ("pinky") toes are the ones most often affected as they typically have more contact with the lining of shoes that may harbor the organism.
The earlier you begin treating a nail infection, the better the chances of success. Topical medications can help, especially if the whole nail is not involved. Over-the-counter versions include Tineacide, Fungoid Tincture, and Mycocide NS. One product I find of particular promise is Formula 3, a newly patented oil-based antifungal capable of penetrating the active ingredient through the nail to the nail bed. All of these products require application twice daily for a minimum of three months, some as long as one year.
If you don't begin to see improvement in two to three months or if the toenail gets worse, see your doctor. When topical medications prove ineffective, physicians, or podiatrists (where permitted by law), often recommend oral medications, which are available by prescription. Two widely used drugs are Itraconazole and Lamisil.
Occasionally, when the nail is more white than yellow, the infection may be caused by yeast, a special type of fungus. In this case, another prescription drug called Spectrazole is often used. Recently, the FDA approved Penlac that contains ciclopiroxolamine, a prescription nail polish that contains an antifungal drug; however, it was deemed effective (defined as a "complete cure" or having reduced the area of nail involvement by 90%) in less than 10% of the people who used it.
The best way to prevent a fungal infection (or prevent one from spreading) is to keep your feet and toes clean and dry.
Try these precautions:
Wear cotton or wool socks and change them frequently.
Air out your shoes after use: Open up laces, loosen the tongue, and remove insoles to promote thorough drying.
Dry your feet well after washing and use ample foot powder, if needed, especially between the toes.
Avoid walking barefoot in public bathrooms or shower areas. Better yet, try wearing waterproof sandals in the shower.
Best of luck and a speedy recovery from the nuisance of toenail fungus,
Dr. James K Budd, DPM (Retired)