Thickened, discolored nails happen often with age. One of the most common causes is a fungal infection called onychomycosis, which strikes about 50 percent of people over age 70.
Small cracks in the nail or the skin around it allow the fungus to enter the nail, and closed-toe shoes then provide a warm, moist environment for the fungus to thrive.
You can try treating the infection with over-the-counter antifungal nail creams and ointments, but if you have a persistent infection or have diabetes, immune system disorders, or poor circulation, it’s important to see your primary care doctor, dermatologist, or podiatrist. Prescription treatments may include oral antifungal drugs such as terbinafine (Lamisil) and itraconazole (Sporanox), antifungal nail polish or creams, and/or removal of the damaged part of the nail in a process called debridement.
Use these steps to minimize the risk for fungal infections: