Obsessive–compulsive disorder (OCD) is a condition in which patients experience persistent unwanted thoughts, ideas, or feelings (obsessions), which triggers them to perform an action repeatedly (compulsions), such as washing hands, checking objects, or cleaning, which may interfere with everyday tasks and interpersonal relationships . OCD has a high impact on the patient’s quality of live, and has been associated with an enhanced prevalence of psychiatric comorbidities , as well as dermatological disorders such as cellulitis . OCD is widely prevalent in adults, adolescents, and children worldwide . In most cases, the disease is detected by the age of 19 years, and it occurs earlier in males than in females .
Onychotillomania is an unusual and often misunderstood behavioral tendency that affects the nail apparatus. Patients are identified by an obsessive or irrepressible impulse to repeatedly damage their nails, either with their fingers or with other objects, resulting in obvious and even irreparable self-destruction of the nail unit . A person with this impulse may be conscious or unconscious of its appearance [7, 8]. Regarding clinical manifestations, onychotillomania is characterized by various nonspecific findings such as unusual nail morphology, nail plate injury, and periungual skin irritation . Furthermore, characteristics that are not present in other nail disorders, such as loss of the nail plate, presence of several obliquely directed nail bed hemorrhages, gray coloration of the nail plate, and wavy lines, may also be observed . It affects 0.9% of the global population, and can cause permanent nail deformation, melanonychia, and infections . Onychotillomania diagnosis requires an understanding of the patient’s clinical history, as treatment methods may include behavioral treatments and psychiatric drugs .
Approximately 33% of individuals with dermatological disorders are affected by emotional and psychological variables . It is possible that a mental illness may be caused by an underlying dermatological problem, as in the case of onychotillomania . Few studies have reported an association between OCD and onychotillomania [13, 14]. In psychiatry, onychotillomania is considered an impulse control disorder, similar to OCD, compulsive gambling, and kleptomania . It has also been categorized as a habitual deformity that may develop due to mental and emotional stress, or as a type of OCD . Although onychotillomania was not listed in the Diagnostic and Statistical Manual of Mental disorders-5 or the International Classification of Diseases-10 as a separate disorder, it can be considered as a body-focused repetitive behavioral disorder that includes other traits, such as nail biting and cheek chewing. As onychotillomania is often associated with serious depression and OCD, a correct diagnosis of the condition is crucial but difficult. Importantly, onychotillomania may also indicate the presence of other mental problems such as OCD  and depression .
Individuals suffering from onychotillomania should consider seeking treatment for any underlying psychological illnesses. In addition to onychotillomania, onychophagia and trichotillomania-like symptoms are among the most prevalent dermatological manifestations of OCD . In a study involving 509 patients with OCD, 56 patients had nail-biting habits, which is substantially higher than that in the general population . However, as hypothesized, OCD is not the underlying psychopathology for every patient with onychotillomania. Before concluding that a patient with onychotillomania has OCD, it is necessary to rule out alternative psychiatric diagnoses, such as delusions or simple habit disorders .
After psychiatric evaluation and diagnosis, it is critical that the underlying mental disease be identified and treated with psychotropic medications . Individual psychotherapy and behavioral therapy are the two most commonly used therapies for OCD. Additionally, oral drugs are often used to treat OCD.
Onychotillomania typically presents with therapeutic problems. It is a chronic and difficult-to-manage condition, largely because of it has a psychocutaneous character as well as a high tendency to interact with underlying neuropsychiatric diseases or other behavioral disorders . Reports have shown that cognitive behavioral therapy, physical-barrier approaches, and pharmaceutical treatments have some advantages, although no major clinical studies have investigated the effectiveness of these therapies. Onychotillomania remains a clinical and therapeutic issue for dermatologists, pediatricians, internists, and psychiatrists in practice because there are no evidence-based treatment techniques .
Various methods have been reported for treating onychotillomania. Nonpharmacological treatments include covering the nails or toes with physical barriers, such as an Unna boot [7, 21], gloves, or bandages , and cyanoacrylate adhesive . Psychotherapy is also used and is mainly directed towards performing a competing response, such as gripping and pulling the hands , or acceptance-enhanced behavior therapy, including habit reversal and stimulus control. 
The effectiveness of pharmacological treatments, consisting of the administration of various drugs such as N-acetylcysteine [26, 27], intravenous triamcinolone acetonide followed by a topical combination of calcipotriol and betamethasone dipropionate , citalopram, and zolpidem hemitartrate , as well as behavioral treatment  have been reported for onychotillomania.