(See also Overview of Nail Disorders Overview of Nail Disorders A variety of disorders can affect nails, including deformities, trauma, infections of the nail, paronychia, retronychia, and ingrown toenails. Nail changes may occur in many systemic conditions... read more .)
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 Pincer nail deformity Deformities are often considered together with dystrophies, but the two are slightly different; deformities are generally considered to be gross changes in nail shape, whereas dystrophies are... read more 
). Sometimes an underlying osteochondroma Osteochondroma Benign bone tumors include benign giant cell tumors of bone, chondroblastomas, chondromyxoid fibromas, enchondromas, nonossifying fibromas, osteoblastomas, osteochondromas, and osteoid osteomas... read more 
is responsible, especially in the young. In older people, peripheral edema is a risk factor. Eventually, infection can occur along the nail margin (paronychia Acute Paronychia Paronychia is infection of the periungual tissues. Acute paronychia causes redness, warmth, and pain along the nail margin. Diagnosis is by inspection. Treatment is with antistaphylococcal antibiotics... read more 
).
Symptoms and Signs
Pain occurs at the corner of the nail fold or, less commonly, along its entire lateral margin. Initially only mild discomfort may be present, especially when wearing certain shoes. In chronic cases, granulation tissue becomes visible, more often in the young.
Diagnosis
Clinical evaluation
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 Osteochondroma Benign bone tumors include benign giant cell tumors of bone, chondroblastomas, chondromyxoid fibromas, enchondromas, nonossifying fibromas, osteoblastomas, osteochondromas, and osteoid osteomas... read more . 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.
Treatment
Usually nail excision and destruction of adjacent nail matrix
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. (See also How To Treat an Ingrown Toenail How To Treat an Ingrown Toenail An ingrown toenail is incurvation or impingement of a nail border into its adjacent nail fold. (See also Ingrown Toenail.) Inflammation and/or infection around the ingrown toenail Confirm that... read more .) Phenol should not be used if there is arterial insufficiency.
