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.
Toenails, like hair, are composed of dead protein, not living tissue. Toenails grow longer when the nail root, which is located under the skin at the base of the nail, produces more nail material, moving the existing nail forward toward the end of the toe. When subjected to physical stresses, the nail root can produce an incorrectly formed nail that ends up growing into the surrounding tissue. The nail first presses against the tissue, causing irritation and sensitivity. As it continues to grow, the malformed nail pierces the skin, allowing germs and bacteria to infect the area.