A systematic review of the published literature pertaining to tinea pedis in homeless populations was conducted. Although there is a sparsity of region-specific descriptive data, studies have reported high rates of tinea pedis and other lower extremity problems across different settings. Among dermatophyte infections, tinea pedis was disproportionately higher in homeless patients compared to the general population. Unfortunately, studies detailing tinea pedis and other dermatophyte infections typically do not distinguish between unsheltered and sheltered homeless patients.
Most of the epidemiological data evaluated in this study includes the United States as a whole, and does not account for regional categories and climate, such as the South, Midwest, and North. There has not been an adequate comparison of the influence of large-scale regional factors (climate, socioeconomics) on the development of foot dermatophyte infections . It is likely that regions with higher humidity and rainfall would have an increased prevalence of conditions like immersion foot and tinea pedis compared to less tropical areas . South Florida’s tropical environment and high indigent population make it likely to have high proportions of tinea pedis.
Certain studies in Europe demonstrated a higher risk of tinea pedis in unhoused individuals compared to their housed counterparts . However, the Achilles project from 20 European countries showed approximately 35% of patients encountered from the general population had tinea pedis. Expanded scope of research is needed to properly assess PEH tinea pedis frequencies across multiple European countries. Similar studies have not been conducted in the Southeastern United States, many unknown variations in geography, demographics, and social programs could conceal a rising epidemic. Notwithstanding, the rates of tinea pedis among sheltered homeless individuals in the United States are still higher than those of the general population, likely due to a combination of crowded living conditions, inadequate hygiene facilities, and a lack of resources .
Comparing tinea pedis prevalence between regions
Due to tinea pedis being the most common fungal infection worldwide, prevalence as well as etiology also varies between regions. For example, interdigital tinea pedis in a Senegalese study was found to be approximately 5.6% of all mycological complaints, of which Candida albicans was the most common pathogen (39%) . On the other hand, an Egyptian study reported T. rubrum as the most common isolate in tinea pedis (53.4%) . Limited data currently exists on the exact regional differences in tinea pedis within North America. The data for tinea pedis and other skin infections is even more sparse for homeless individuals, even though they are at a much greater risk for such conditions compared to the general population . One of the largest studies conducted by Badiaga et al. in France found a statistically significant association between tinea pedis and homelessness. Among 498 sheltered homeless patients encountered, 3.2% (N = 16) were diagnosed with tinea pedis, which was lower than the general population at 34.9% (N = 24,603) as seen in the Achilles Project [16, 47]. This may indicate a limited and skewed sample size. The Achilles Project also included more than 70,000 patients presenting to dermatologists, more likely to have skin pathology compared to a truly general sample of the population. Similar studies were conducted in California and Boston which found tinea pedis prevalence among sheltered homeless patients to be 3.1% and 38%, respectively . These studies were conducted among patients in a sheltered setting but did not sufficiently sample unsheltered homeless patients. The evident differences in health outcomes, living conditions, and healthcare utilization between sheltered and unsheltered individuals suggest that a comparison of tinea pedis could be significantly different between the two groups.
Additionally, there have not been any satisfactory studies detailing the epidemiology of tinea pedis among PEH in the Southeastern United States or the South Florida region. Studies conducted in France, California, and Boston would have very limited generalizability for a tropical climate like South Florida, as well as an unequal government funding and support for homeless rehabilitation programs. Particularly in Miami-Dade County, there is an extreme necessity for adequate characterization of pedal dermatophyte infections as it has the highest numbers of homeless individuals in the entirety of Florida, (approximately 4,300 out of a total of roughly 27,000 in the state ). Moreover, these data do not adequately account for undocumented homeless individuals, and with the moratorium on evictions in South Florida lifted in September and October 2021, it is likely that this number will increase considerably .
Overall difference in healthcare outcomes between sheltered and unsheltered PEH
Literature detailing the health outcomes of homeless individuals typically does not distinguish between sheltered and unsheltered homelessness. However, there are significantly different health parameters between the two groups which require further attention. For example, a study in North Texas over 24 months detailed significantly different levels of healthcare service use between unsheltered (94.2%) and sheltered (83.5%) patients . Additionally, the difference in emergency department usage for unsheltered (72.5%) versus sheltered (59.8%) patients was statistically significant. The increased likelihood of chronic physical health conditions in unsheltered homeless patients suggests that categorizing both groups under the umbrella of homelessness can conceal crucial health outcomes and differences. This can also extend to the prevalence and morbidity/mortality of tinea pedis among the two groups .
The lack of reliable hygiene, laundry, and health facilities make it likely that unsheltered homeless patients would have higher rates of dermatophytosis. However, it is worth considering whether the crowded conditions in shelters make it easier for the spread of cutaneous fungal infections. Historically underfunded organizations may also be unable to appropriately sanitize their facilities, leading to the spread of tinea pedis particularly among showers and common areas. However, the most important predictor of homeless health has consistently been access to shelter. Improved access to healthcare and appropriate nutrition may offset this spread and have an overall beneficial effect on the health of sheltered patients as compared to their unsheltered counterparts.
Tinea pedis-associated infections and complications
In developed nations, fungal interdigital tinea pedis is the most frequent dermatomycosis . Residence in warm climates with a concurrently high humidity level causes increased sweating, particularly in the feet. This can lead to washing away of protective surface lipids, thereby creating a window for dermatophyte proliferation . The host response to infection is epidermal proliferation, causing skin scaling and thickening. Additionally, fissuring and maceration can be observed in the interdigital spaces, usually around the fourth or fifth toes. Such disruptions in the epidermal barrier permit other organisms such as streptococci to colonize interdigital spaces. Therefore, symptomatic tinea pedis can also be seen due to the interaction between fungi and bacteria . The downstream consequences include an increased likelihood of cellulitis, abscesses, and even osteomyelitis. The initial fungal infection can therefore serve as an opportunity for more severe, systemic infections. For this reason, proper foot health and evaluation of both sheltered and unsheltered homeless patients are vital . Early treatment of such infections before progression can avoid the development of potentially life-threatening complications. This is particularly important for unsheltered homeless patients, for whom skin and soft tissue infections are one of the most common reasons for emergency department visits.
Other foot infections associated with tinea pedis
Tinea pedis does not necessarily exist in isolation, but often in conjunction with various other lower extremity pathologies . Conditions such as vascular insufficiency, diabetes, and immune dysfunction can predispose towards dermatophyte infections . Cell-mediated immunity has been found to be crucial in mounting an appropriate response to dermatophytes.
There are disproportionately higher rates of lower extremity lesions in homeless individuals compared to the general population  and this can predispose them to dermatophyte infections. Recurrent episodes of cellulitis are often associated with underlying tinea pedis infection, and diabetic foot ulcers can also be exacerbated by the presence of dermatophytes. Pressure ulcers from impaired proprioception as well as dysautonomia can lead to an increased dermatophyte colonization and accelerate the process of epidermal dysfunction. Sheltered and unsheltered homeless individuals have also been found to suffer from disproportionate rates of immersion foot, calluses, pitted keratolysis, and foot infections . When coupled with inadequate living conditions and malnutrition, such conditions can contribute to skin ulcers, chronic non-healing wounds, and osteomyelitis [51–53].
An important consideration in refractory cases of infectious lower extremity dermatologic conditions is the potential for reinfection. Onychomycosis is often caused by the same dermatophytes as tinea pedis, and infections can spread from the nails to the skin and vice-versa [45–49]. This means that there may not be complete resolution until both infections are treated. Therefore, in situations where patients have tinea pedis infections as well as onychomycosis or other lower extremity dermatologic conditions, thorough treatment of all conditions should be initiated to decrease risk of complications and re-infection.
1. Evaluation of tinea pedis when treating homeless patients
Although the specific, regional data may be incomplete, it has been established over multiple studies that PEH are more likely than the general population to suffer from dermatophytoses [11–18]. Therefore, particularly in regions with high levels of humidity such as South Florida, tinea pedis should be evaluated among all patients, especially those presenting with foot concerns. Careful examination of the plantar surface, interdigital surfaces, and toenails should be performed to rule out any other pathology that could contribute to recurrent tinea pedis such as onychomycosis [32–37]. More research is currently needed for this high-risk patient group in the South Florida region, particularly due to the tropical climate, lack of sufficient shelters, and increased likelihood of tropical and zoonotic infections .
2. Recognizing the differing health outcomes between sheltered and unsheltered homeless patients
Research conducted thus far on dermatophyte infections in homeless populations have mostly used sheltered samples as study subjects. The significantly higher levels of overall disease burden in unsheltered homeless patients suggests that they are more likely to use emergency healthcare services compared to their sheltered counterparts [23–27]. Therefore, future research should be directed towards stratifying these two groups in order to better understand the measures that can best suit their health needs. It would also be expected for unsheltered homeless patients to have higher susceptibility to tinea pedis, due to a lack of access to hygiene facilities and increased likelihood of suffering from chronic illnesses. In addition, specific treatment and treatment success rates between the two groups may be different and warrants further investigation for best practice recommendations in treatment of tinea pedis among USH patients.
3. Keeping tinea pedis-associated complications in mind
Various environmental, health, and hygiene factors play a definitive role in the pathogenesis of dermatophyte infection, particularly for tinea pedis. Refractory tinea pedis can occur due to autoinfection from other affected areas, such as in the case of tinea cruris, tinea capitis, and tinea corporis [14–18]. Additionally, tinea pedis infections may not follow an indolent course, high-risk patients are more likely to suffer from complications such as cellulitis, osteomyelitis, ulcerations, and chronic non-healing wounds . Tinea pedis can also facilitate a portal for further infection. Pre-emptive treatment could prevent these complications from arising, thereby improving the health of this high-risk patient group and also potentially decrease emergency department utilization. Therefore, when treating both sheltered and unsheltered homeless patients, it is necessary to keep these potential complications in mind.
4. Ensuring adequate overall foot health while treating tinea pedis
The feet of unsheltered PEH are often in near-constant contact with the outside environment. Traumatic injury, ingrown toenails, and pitted keratolysis can lead to a disruption of the epidermal barrier even more so than tinea pedis infections. Providing measures to maintain foot health and hygiene is paramount in ensuring adequate treatment [55, 56]. Simply providing antifungal treatment may not necessarily lead to better long-term results and thus preventative care is vital. Overall foot health can be maintained by regular examination and cleaning, as well as wearing clean and protective footwear [57–60]. PEH patients with conditions such as diabetes often find immense difficulty in finding appropriate insulin supplies and often suffer from poor blood glucose control. As a result, diabetic foot ulcers can be observed rather frequently . Addressing overall foot health can be vital in ensuring that other severe conditions can also be treated or avoided, if possible. Certain outreach events such as community-based foot-washing events should be more frequently employed in order to assess the overall health and foot conditions of the patients in unsheltered settings and connect high-risk patients to more immediate care and careful follow up.
5. Consistent, low-cost measures to keep dermatophytoses in check: Miami Street Medicine Clinic’s work
The additional provision of clean, cotton socks as well as reliable facilities for hygiene can definitively prevent recurrences of this condition. For example, some preliminary data by the Miami Street Medicine clinic describes the distribution of socks and antifungal powder as being widely popular among unsheltered patients . This added effect of increased patient compliance in a resource-limited setting can be a way to manage this problem without large-scale interventions. It cannot be feasibly expected for public housing facilities or shelter facilities to immediately increase their census, so sustained outreach programs for unsheltered patients can build rapport and establish a longitudinal care relationship.