Nail biting

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Nail biting
Nail and cuticle bitting.JPG
Fingers of a nail-biter.
Classification and external resources
Specialty Pediatrics
ICD-10 F98.8 (ILDS F98.810)
ICD-9-CM 307.9
DiseasesDB 31465
MeSH D009259

Nail biting, also known as onychophagy or onychophagia, is an oral compulsive habit. It is sometimes described as a parafunctional activity, the common use of the mouth for an activity other than speaking, eating, or drinking.


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] Nevertheless, the frontier pathological nail biting is not clear.[2]

Signs and symptoms[edit]

Nail biting usually leads to deleterious effects in fingers, but also mouth and more generally the digestive system. These consequences are directly derived from the physical damage of biting or from the hands becoming an infection vector. Moreover, it can also have a social impact.[2]

The ten fingernails are usually equally bitten to approximately the same degree.[3] 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][3] In rare cases, fingernails may become severely deformed after years of nail biting due to the destruction of the nail bed.[2][4]

Nail biting is also related to oral problems, such as gingival injury, and malocclusion of the anterior teeth.[2][5] It can also transfer pinworms or bacteria buried under the surface of the nail from the anus region to the mouth.[2] When the bitten-off nails are swallowed, stomach problems can develop.[5]

Nail-biting is also associated to guilt and shame feelings in the nail biter, a reduced quality of life, and increased stigmatization in the inner family circles or at a more societal level.[2][6]

Related disorders[edit]

Other body-focused repetitive behaviors include excoriation disorder (skin picking), dermatophagia (skin biting), and trichotillomania (the urge to pull out hair), and all of them tend to coexist with nail biting.[2][7] As an oral parafunctional activity, it is also associated with bruxism (tooth clenching and grinding), and other habits such as pen chewing and cheek biting.[8]

In children nail biting most typically co-occurs with attention deficit hyperactivity disorder (75% of nail biting cases in a study),[2] but also with a plethora of other psychiatric disorders including oppositional defiant disorder (36%), and separation anxiety disorder (21%).[2] It is also more common among children and adolescents with obsessive–compulsive disorder.[2][9] Nail biting appeared in a study to be more common in men with eating disorders than those without them.[10]


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.[11]

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.[12] A study in children showed that results with HRT were superior to either no treatment at all or the manipulation of objects as an alternative behavior, which is another possible approach to treatment.[13] In addition to HRT, stimulus control therapy is used to both identify and then eliminate the stimulus that frequently triggers biting urges.[14] Other behavioral techniques that have been investigated with preliminary positive results are self-help techniques,[15] and the use of wristbands as non-removable reminders.[16]

Another treatment for chronic nail biters, is using a dental deterrent device that disables the front teeth from making any damage to the nails and the surrounding cuticles. After about two months the device leads to a full oppression of the nail biting urge. The nail biting deterrent device was invented in 2009.

Evidence on the efficacy of drugs is very limited and they are not routinely used.[17] A small double-blind randomized clinical trial in children and adolescents indicated that N-acetylcysteine, a glutathione and glutamate modulator, could be more effective than placebo in decreasing the nail-biting behavior, albeit it was only useful in the short term.[17]

Finally nail cosmetics can help to ameliorate nail biting social effects.[18]

Independently of the method used, parental education is useful in the case of young nail biters to maximize the efficacy of the treatment programs, as some conducts by the parents or other family members may be helping to perpetuate the problem.[2] For example, punishments have been shown to be not better than placebo, and in some cases may even increase the nail biting frequency.[2]


While it is rare before the age of 3,[2] about 30 percent of children between 7 and 10 years of age and 45 percent of teenagers engage in nail biting.[2][3] Finally, prevalence decreases in adults.[2] Figures may vary between studies, and could be related to geographic and cultural differences.[2] The proportion of subjects that have ever had the habit (lifetime prevalence) may be much higher than the proportion of current nail-biters (time-point prevalence).[19] Although it does not seem to be more common in either sex, results of epidemiological studies on this issue are not fully consistent.[2] It may be underrecognized since individuals tend to deny or be ignorant of its negative consequences, complicating its diagnosis.[7] Having a parent with a mental disorder is also a risk factor.[2]


  1. ^ "Impulse control disorder". SteadyHealth. 30 December 2010. Retrieved 28 April 2012. 
  2. ^ a b c d e f g h i j k l m n o p q r s Ghanizadeh, A (Jun 2011). "Nail biting; etiology, consequences and management.". Iranian journal of medical sciences 36 (2): 73–9. PMC 3556753. PMID 23358880. 
  3. ^ a b c Leung AK, Robson WL (1990). "Nailbiting". Clin Pediatr (Phila) 29 (12): 690–2. doi:10.1177/000992289002901201. PMID 2276242. 
  4. ^ Jabr FI (September 2005). "Severe nail deformity. Nail biting may cause multiple adverse conditions". Postgrad Med 118 (3): 37–8, 42. doi:10.3810/pgm.2005.09.1712. PMID 16201307. 
  5. ^ a b Tanaka OM, Vitral RW, Tanaka GY, Guerrero AP, Camargo ES (August 2008). "Nailbiting, or onychophagia: a special habit". Am J Orthod Dentofacial Orthop 134 (2): 305–8. doi:10.1016/j.ajodo.2006.06.023. PMID 18675214. 
  6. ^ Pacan, P; Reich, A; Grzesiak, M; Szepietowski, JC (Feb 17, 2014). "Onychophagia is Associated with Impairment of Quality of Life.". Acta dermato-venereologica 94: 703–6. doi:10.2340/00015555-1817. PMID 24535041. 
  7. ^ a b Bohne A, Keuthen N, Wilhelm S (2005). "Pathologic hairpulling, skin picking, and nail biting". Ann Clin Psychiatry 17 (4): 227–32. doi:10.1080/10401230500295354. PMID 16402755. 
  8. ^ Cawson RA, Odell EW, Porter S. (2002). Cawson's essentials of oral pathology and oral medicine. (7th ed.). Edinburgh: Churchill Livingstone. p. 66. ISBN 0443071063. 
  9. ^ Grant JE, Mancebo MC, Eisen JL, Rasmussen SA (January 2010). "Impulse-control disorders in children and adolescents with obsessive–compulsive disorder". Psychiatry Res 175 (1–2): 109–13. doi:10.1016/j.psychres.2009.04.006. PMC 2815218. PMID 20004481. 
  10. ^ Mangweth-Matzek B, Rupp CI, Hausmann A, Gusmerotti S, Kemmler G, Biebl W (2010). "Eating disorders in men: current features and childhood factors". Eat Weight Disord 15 (1–2): e15–22. PMID 20571316. 
  11. ^ Allen KW (March 1996). "Chronic nailbiting: a controlled comparison of competing response and mild aversion treatments". Behav Res Ther 34 (3): 269–72. doi:10.1016/0005-7967(95)00078-X. PMID 8881096. 
  12. ^ Bate, KS; Malouff, JM; Thorsteinsson, ET; Bhullar, N (July 2011). "The efficacy of habit reversal therapy for tics, habit disorders, and stuttering: a meta-analytic review.". Clinical Psychology Review 31 (5): 865–71. doi:10.1016/j.cpr.2011.03.013. PMID 21549664. 
  13. ^ Ghanizadeh, A; Bazrafshan, A; Firoozabadi, A; Dehbozorgi, G (Jun 2013). "Habit Reversal versus Object Manipulation Training for Treating Nail Biting: A Randomized Controlled Clinical Trial.". Iranian journal of psychiatry 8 (2): 61–7. PMC 3796295. PMID 24130603. 
  14. ^ Penzel, Fred. "Skin picking and nail biting: related habits". Western Suffolk Psychological Services. Retrieved 2008-03-22. 
  15. ^ Moritz, S; Treszl, A; Rufer, M (Sep 2011). "A randomized controlled trial of a novel self-help technique for impulse control disorders: a study on nail-biting.". Behavior modification 35 (5): 468–85. doi:10.1177/0145445511409395. PMID 21659318. 
  16. ^ Koritzky, G; Yechiam, E (Nov 2011). "On the value of nonremovable reminders for behavior modification: an application to nail-biting (onychophagia).". Behavior modification 35 (6): 511–30. doi:10.1177/0145445511414869. PMID 21873368. 
  17. ^ a b Ghanizadeh, A; Derakhshan, N; Berk, M (2013). "N-acetylcysteine versus placebo for treating nail biting, a double blind randomized placebo controlled clinical trial.". Anti-inflammatory & anti-allergy agents in medicinal chemistry 12 (3): 223–8. doi:10.2174/1871523011312030003. PMID 23651231. 
  18. ^ Iorizzo M, Piraccini BM, Tosti A (March 2007). "Nail cosmetics in nail disorders". J Cosmet Dermatol 6 (1): 53–8. doi:10.1111/j.1473-2165.2007.00290.x. PMID 17348997. 
  19. ^ Pacan, P; Grzesiak, M; Reich, A; Kantorska-Janiec, M; Szepietowski, JC (Jan 2014). "Onychophagia and onychotillomania: prevalence, clinical picture and comorbidities.". Acta dermato-venereologica 94 (1): 67–71. doi:10.2340/00015555-1616. PMID 23756561.