www.foothouse.co.uk What is an Ingrown Toenail? An ingrown toenail affects the large toe in most cases but can also affect the other toes. An ingrown toenail occurs when a sliver of nail pierces the flesh at the side of the nail. The condition can be extremely painful and occasionally the toe can become infected. If an infection is present, the toe will become very inflamed and can produce pus and blood. What causes it? Toenails come in all shapes