(See also Overview of Nail Disorders.)
Causes of ingrown toenail include tight shoes, abnormal gait (eg, toe-walking), bulbous toe shape, excessive trimming of the nail plate, or congenital variations in nail contour (eg, congenital pincer nail deformity). Sometimes an underlying osteochondroma is responsible, especially in the young. In the elderly, peripheral edema is a risk factor. Eventually, infection can occur along the nail margin (paronychia).
Redness, swelling, and pain may also suggest concurrent paronychia. In young patients (eg, < 20 years) with recurrent ingrown toenails, x-rays should be considered to exclude underlying osteochondroma. In the absence of an ingrown toenail, apparent granulation tissue around the toe suggests the possibility of amelanotic melanoma, which is often overlooked; biopsy is necessary.
In mild cases, inserting cotton between the ingrown nail plate and painful fold (using a thin toothpick) may provide immediate relief and, if continued, correct the problem. If the shoes are too tight, a larger toe box is indicated.
In most cases, however, particularly with paronychia, excision of part or occasionally all of the ingrown toenail after injecting a local anesthetic is the only effective treatment. After excision, a flexible tube can be used to separate the nail plate and painful fold and allow healing. If ingrown toenails recur, sodium hydroxide or phenol is applied to permanently destroy the nearby lateral nail matrix. Phenol should not be used if there is arterial insufficiency.