Nail biting is considered an impulse control disorder in the DSM-IV-R, and is classified under obsessive-compulsive and related disorders in the DSM-5. The ICD-10 classifies it as "other specified behavioral and emotional disorders with onset usually occurring in childhood and adolescence."
Signs and symptoms
Biting nails can lead to broken skin on the cuticle. When cuticles are improperly removed, they are susceptible to microbial and viralinfections such as paronychia. Saliva may then redden and infect the skin.
The most common treatment, which is cheap and widely available, is to apply a clear, bitter-tasting nail polish to the nails. Normally denatonium benzoate is used, the most bitter chemical compound known. The bitter flavor discourages the nail-biting habit.
Behavioral therapy is beneficial when simpler measures are not effective. Habit Reversal Training (HRT), which seeks to unlearn the habit of nail biting and possibly replace it with a more constructive habit, has shown its effectiveness versus placebo in children and adults. In addition to HRT, stimulus control therapy is used to both identify and then eliminate the stimulus that frequently triggers biting urges.
Finally nail cosmetics can help to ameliorate nail biting social effects.
About 30 percent of children between 7 and 10 years of age and 45 percent of teenagers engage in nail biting. The ten fingernails are usually equally bitten to approximately the same degree. It may be underrecognized since individuals tend to deny or be ignorant of its negative consequences, complicating its diagnosis.