Ingrown toenails are one of the leading causes of foot pain for which people seek medical treatment. An ingrown toenail occurs when one or both sides of the nail grow into the surrounding skin. As the nail grows, its edge presses into and can eventually pierce the skin along the nail's border. People of all ages and backgrounds can suffer from ingrown toenails, though severe cases are most often seen in young adults. Because they are subject to more pressure and trauma, the big toe on each foot is more likely than the others to develop an ingrown toenail.
Ingrown toenails are almost always painful.
They may also appear red and warmer than the surrounding skin. When the toenail pierces the skin, bacteria enter the wound, causing the area to become infected. Signs of infection include pain, swelling, redness and pus drainage. If left untreated, an infected ingrown toenail could lead to an infection in the bone. Extreme cases can result in the loss of the toe or even the leg.