Onychophagia describes a habit of nail biting in which the nails and adjacent skin are chewed. The fingernails are the preferred site, although occasionally the toenails are involved. Patients usually bite the nails on both hands.

Nail-biting behavior can be made worse when the patient is anxious, bored, or working on complex tasks. It improves with social interaction. It may also improve when the behavior is pointed out.

Nail biting often begins in childhood or adolescence, but cases of adult-onset nail biting do occur. Nail-biting behavior typically lasts for approximately 10 years; however, it may persist into adulthood.

Onychophagia may be associated with an underlying psychiatric disease such as obsessive-compulsive disorder, anxiety disorder, impulse control disorder, anorexia nervosa, or bulimia nervosa. There is a partial genetic component of onychophagia, as many nail biters have at least one family member with this habit.

Onychophagia has a negative effect on quality of life. Nails tend to be both very short and uneven. In more severe cases, cuticles are absent or ragged and nail folds are frayed. Splinter hemorrhages are common findings. Sequelae include increased rate of nail plate growth, shortening and disappearance of the nail bed, longitudinal melanonychia, and paronychia. Oral complications are gingival swelling, malocclusion of the teeth, temporomandibular joint syndrome, and infections following oral surgery.

Rare complications are osteomyelitis and herpetic whitlow.

Onychophagia may facilitate the spread of verruca.

Related topics: onychotillomania, trichotillomania