An ingrown toenail, medically termed onychocryptosis, is a painful condition affecting any one of the nails on the feet. However, an ingrown toenail most often occurs on the big toe. The side and/or front of an ingrown toenail curl and grow into the skin of the toe, causing redness, swelling, and in some cases, bleeding or infection.

Mild pain or pressure in the toe is the first symptom of an ingrown toenail. If allowed to progress, the pain of the ingrown toenail will intensify, followed by redness. When a large portion of the toenail has become ingrown, it is visible, but in some cases, a shard of the toenail is the only part that becomes ingrown. Though less obvious than a large ingrown toenail, it can be just as painful, if not more so. This type of ingrown toenail might feel as though the skin is being pierced by a knife.

Sometimes, an ingrown toenail can become infected. The symptoms of an infected ingrown toenail may include warmth around the affected area, raised or protruding skin, and puss or oozing around the nail. If left untreated, an infected ingrown toenail can spread, causing further complications.

An ingrown toenail can develop for a variety of reasons, and some people are more prone to the condition than others. The most common cause of an ingrown toe nail is shoes or socks that are too tight. Improperly fitting shoes can place pressure on the toenail, preventing it from growing normally. Certain methods of nail trimming can also cause an ingrown toenail. Cutting the nails too short or in an angular shape instead of straight across can cause the nail to become ingrown.

Genetics also play a role in the likelihood of developing an ingrown toenail. Incurvated nails are nails that naturally curve from side to side rather than lying flat on the nail bed. This type of nail curves deep into the skin fold and may often result in an ingrown toenail. Although usually inherited, incurvated nails can also be the result of injury or trauma to the toe.

Some health conditions can also contribute to an ingrown toenail. People who suffer from diabetes, poor circulation, or other illnesses that cause edema are often prone to an ingrown toenail. This is because fleshy or swollen feet protrude around the nail, causing it to grow into the skin. Ingrown toenails have a tendency to recur even after treatment, so it is important for people who have had an ingrown toenail in the past to take preventive measures for the future.