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Title: Onychophagia  
Author: World Heritage Encyclopedia
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Subject: Trichotillomania, Dermatillomania, Onychotillomania, Body-focused repetitive behavior
Publisher: World Heritage Encyclopedia


Nail biting
Classification and external resources
10 9 307.9

Onychophagia (also onychophagy) or nail biting, is a common oral compulsive habit (sometimes described as a parafunctional activity) in children and adults.


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."[1]

Health consequences

Biting nails can lead to broken skin on the cuticle. When cuticles are improperly removed, they are susceptible to microbial and viral infections such as paronychia. Saliva may then redden and infect the skin.[2]

Nail biting is also related to dental problems, such as gingival injury and malocclusion of the anterior teeth.[3][4]

It can also transfer pinworms or bacteria buried under the surface of the nail from the anus region to the mouth.[5][6] When the bitten-off nails are swallowed stomach problems can develop.[4]

Medical literature reports cases of fingernails being severely deformed after years of nail biting.[7]


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.[8]

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.[9] In addition to HRT, stimulus control therapy is used to both identify and then eliminate the stimulus that frequently triggers biting urges.[10]

Finally nail cosmetics can help to ameliorate nail biting social effects.[11]


About 30 percent of children between 7 and 10 years of age and 45 percent of teenagers engage in nail biting.[2] The ten fingernails are usually equally bitten to approximately the same degree.[2] It may be underrecognized since individuals tend to deny or be ignorant of its negative consequences, complicating its diagnosis.[12]

Related disorders

Related body-focused repetitive behaviors include dermatillomania (skin picking), dermatophagia (skin biting), and trichotillomania (the urge to pull out hair).[12] Nail biting appeared in a study to be more common in men with eating disorders than those without them.[13] It is also more common among children and adolescents with obsessive–compulsive disorder.[14] Nail biting is an oral parafunctional activity, and may be associated with bruxism (tooth clenching and grinding), and other habits such as pen chewing and morsicatio buccarum (cheek biting).[15]


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