(See also Overview of Nail Disorders.)
An ingrown nail can result when a deformed toenail grows improperly into the skin or when the skin around the nail grows abnormally fast and engulfs part of the nail. Wearing narrow, ill-fitting shoes and trimming the nail into a curve with short edges rather than straight across can cause or worsen ingrown toenails. Toenails should be cut straight across and not into a curve with short edges.
Ingrown nails may cause no symptoms at first but eventually may become painful, especially when pressure is applied to the ingrown area. The area is usually red and may be warm. If not treated, the area is prone to infection. Once infected, the area becomes more painful, red, and swollen. Pus may accumulate under the skin next to the nail (an infection of the cuticle called paronychia) and drain.
For mildly ingrown toenails, the doctor can gently lift the edge of the nail out from under the surrounding skin and place sterile cotton under the nail until the swelling goes away. Sometimes a flexible tube is inserted between the nail and nail fold (the fold of hard skin at the sides of the nail plate where the nail and skin meet) instead of cotton.
If an ingrown nail requires further attention, the doctor usually numbs the area with a local anesthetic (such as lidocaine), then cuts away and removes the ingrown section of nail. The inflammation can then subside, and the ingrown nail usually does not return.