Individuals experiencing homelessness are known to have a generally worse health outcome than the average population of people. People experiencing homeless (PEH) have higher rates of physical and psychiatric health conditions due to or exacerbated by various factors such as increased exposure to communicable diseases, poor living environments, and unintentional injuries 

Homelessness can be described as the situation of an individual, family, or community without stable, permanent, appropriate housing, or the immediate prospect, means, and ability of acquiring it (1). Individuals experiencing homelessness are known to have a generally worse health outcome than the average population of people. People experiencing homeless (PEH) have higher rates of physical and psychiatric health conditions due to or exacerbated by various factors such as increased exposure to communicable diseases, poor living environments, and unintentional injuries (2). Psychiatric conditions are one of the major health concerns among people experiencing homelessness. The mean prevalence of mental health conditions in PEH living in high-income countries was about 76.2% (3). Dermatologic disease is a frequent cause of morbidity in the PEH. In high-income countries, the prevalence of skin conditions in PEH ranged from 16.6% to 53.5% (4). Homelessness is linked to a 3-fold increased risk of any skin disorder when compared to the general population (5). PEH are less likely to seek medical attention for a variety of reasons including fear of stigmatization or comorbid psychiatric illness.

Psycho-dermatologic conditions addresses the interplay between psychiatric and dermatologic conditions (6). Mental health disorders can showcase itself as a dermatologic symptom such as in the case of trichotillomania, and psychologic stress can increase systemic inflammation predisposing individuals to conditions like seborrheic dermatitis (7,8). On the other hand, the visibility or chronic physical discomfort of certain skin conditions, such as onychomycosis, can lower one’s self-esteem and increase predisposition to depression and anxiety (9). One of the most widely used classification system in psycho-dermatology divides the conditions into three categories: psychophysiologic disorders, primary psychiatric disorders with secondary skin conditions, and primary skin conditions with secondary psychiatric disorders (8). 

Although there has been a general understanding of the association between the skin and the mind, psycho-dermatology is still a relatively new and evolving field. Additionally, there is a scarcity of studies specifically focusing on the psycho-dermatologic conditions that are prevalent amongst PEH. This paper will review some of the prevalent psycho-dermatologic conditions in the homeless population using the classification system discussed above.

Psychophysiologic Disorders:

Psoriasis

Psoriasis is an inflammatory skin condition that is immune-mediated and usually chronic (10). In one study, 14% of PEH had poorly controlled psoriasis compared to the 5.8% of patients with stable housing who had psoriasis (11). This can likely be attributed to the increased life stressors associated with being homeless.

Seborrheic Dermatitis

Seborrheic dermatitis is another chronic inflammatory skin condition that usually affects younger patients and is usually localized to areas like the scalp and face where there is a higher density of sebaceous glands (12). Seborrheic dermatitis is also very prevalent amongst PEH, with one study having about 13.3% PEH with the condition (13). Increased levels of stress and alcohol consumption were found to be strongly associated with seborrheic dermatitis (14).       

Primary Psychiatric Disorders with Secondary Dermatologic Conditions:            

Neurotic Excoriations and Onychotillomania

Neurotic excoriation is a psychiatric condition involving the compulsive and repeated picking of the skin (15). Patients generally scratch, squeeze, or dig at an area of their skin that is easily accessible and had previous trauma (16). Skin picking disorder is strongly associated with other mental health conditions such as depression and generalized anxiety disorder (15). Similarly, onychotillomania is a psychiatric condition in which patients compulsively and repeatedly self-induce trauma to their nails or periungual skin (17). In one case report, a PEH with a history of financial difficulties, major depressive disorder, and substance use disorder developed onychotillomania two months after becoming unsheltered (18).

Delusions of Parasitosis

Trichotillomania is a psychiatric condition in which the patient repeatedly pull out hair from various parts of their body in response to feelings of boredom or stress (19). In one study, 78.8% of the subjects with trichotillomania had another psychiatric condition diagnosed in their lifetime and 38.8% had another current psychiatric condition (20). Diagnosis of trichotillomania is strongly associated with mental health conditions such depression, anxiety, and addictive disorders (20).

Primary Dermatologic Conditions with Secondary Psychiatric Disorders:

Tinea Pedis

Tinea pedis, more commonly known as athlete’s foot, is a chronic dermatophyte fungal infection that primarily affects the soles, toenails, and interdigital regions of the foot (21). Symptoms usually include erosion, fissuring, and peeling, and increases the risk for progression to cellulitis (22). Tinea pedis is one of the most common skin conditions afflicting PEH due to exposure and unhygienic conditions (13). Due to various factors such as financial difficulties and mental health concerns, PEH encounter many obstacles in receiving adequate and equitable care for foot infections (23). As a result, PEH can experience long-term foot discomfort and pain due to their unresolved condition. Studies have shown that patients with chronic foot pain can be twice as likely, when compared to patients without foot pain, to develop depressive symptoms (24).

Pediculosis Corporis (Body Lice) 

Pediculosis corporis is a dermatologic condition involving human body lice that feed on human blood and tend to lay eggs in clothes (25). Body lice is usually spread through direct contact in unhygienic environments and commonly presents as intense pruritis (25). The prevalence of body in PEH can be up to 30% (26, 27). The discomfort and intensity of long-term pruritis can result in secondary anxiety and depressive disorders due to decrease quality of life and feelings of stigmatization (28).

Psycho-dermatologic conditions is a largely underemphasized area in the care for the homeless community. Instead of simply treating these conditions through the lens of one specialty, psycho-dermatology emphasizes the importance of interdisciplinary care and will require the tightknit collaboration of family physicians, psychiatrists, and dermatologists. The increased rates of various psych-dermatologic conditions amongst PEH also highlights a need for better access to community clinics that provide both psychiatric and dermatologic care for these patients. Understanding the interconnection between psychiatric and skin disorders will help us devise better management plans and potentially novel treatments for these complex conditions.