Multiple fungi species can infect the nail. Fungus grows well in warm, moist environments such as showers. Fungus infection is one of the few foot problems that affect more men than women, perhaps because more men walk barefoot in locker rooms. Age is a factor, too. Half the sufferers are people older than 70. Other risk factors include having certain medical conditions such as diabetes, vascular insufficiency and malnutrition.
Infected nails are usually thicker than normal and could be warped or oddly shaped. They can break easily. Nails with fungus might look yellow. Sometimes a white dot shows up on the nail and then gets bigger. When fungus builds up under your nail, it can loosen and even separate the nail from the bed. The fungus can also spread to the skin around your nail.