Toenail problems can affect people of all ages, but tend to be more common in older people. Common causes of fingernail problems include injury, infection and . Text Reference: "Toenail Fungus. . Explore images of dental and oral health diseases as well as cosmetic . Vision is an important aspect of overall health. Fingernail or toenail abnormalities can tell you a lot about your health. They're often . Below are the most likely reasons for the following nail problems: brittle or .