Description of the condition
Tinea pedis - or athlete's foot - is a superficial inflammatory infection of the skin of the feet caused by dermatophyte fungi. Among the fungi responsible for athlete's foot are Trichophyton rubrum, Trichophyton mentagrophytes, and Epidermophyton floccosum ( Hsu 2012; Rinaldi 2000). There are three clinical subtypes of athlete's foot: interdigital, moccasin, and vesiculobullous, with interdigital being the most common (Hsu 2012). This review will focus specifically on the subtype interdigital tinea pedis.
The name 'athlete's foot' was derived from the increased occurrence of the condition among athletes, because of their use of occlusive footwear, which create the ideal conditions for dermatophyte reproduction (Macura 1993). Athlete's foot is characterised by whitish macerated skin and itchy or asymptomatic erythema between the toes, usually in the fourth and fifth spaces. Blisters and cracks in the skin between the toes may cause pain and inflammation of the exposed raw tissue. A concomitant bacterial infection may also be present and require antibiotic treatment. Athlete's foot is typically diagnosed by visual inspection of the lesions, microscopy, and cell culture (Rotta 2012) and may be differentially diagnosed as bacterial or candidal intertrigo, dermatitis, eczema, idiopathic keratoderma, or psoriasis (Rinaldi 2000).
Because of the highly communicable nature of the disease, athlete's foot is one of the most common skin infections, affecting approximately 20% to 25% of the world's population (Havlickova 2008). Despite the development of antifungal agents, the incidence of athlete's foot has increased over the past two decades (Vena 2012). Athlete's foot has been said to occur in roughly 1 in 5 adults, with a prevalence rate of approximately 10% in developed countries (Nelson 2003). This rate is presumably higher in most developing countries whose warm and humid climates are conducive to fungal infection (Nweze 2010). The incidence of athlete's foot has also been shown to increase with age from adolescence (Male 1990), with infection being most common among men between the ages of 25 to 44 years (Panackal 2009; Vena 2012). Individuals at high risk of infection include those who use communal shower and changing rooms (e.g. arenas, swimming pools, fitness centres), those who wear occlusive footwear, those who are obese, and those who are immunosuppressed (e.g. individuals who are HIV positive, diabetic, or organ transplant recipients) (Rinaldi 2000). Studies also suggest that certain occupations that require heavy industrial or military footwear (e.g. miners, soldiers) and industries where workers share common shower and changing areas place people at higher than average risk of infection (Auger 1993; Djeridane 2007; Roberts 1992). People living in institutions and long-term care facilities also show a higher than average prevalence of infection (Roberts 1992) most likely attributable to cross-contamination from communal living.
Treatment and prognosis
The primary treatment for athlete's foot includes topical antifungal medications, applied once or twice daily (Gupta 2008). With appropriate treatment, athlete's foot is usually eradicated within two to four weeks; however, reinfection is possible (Gupta 2008). The condition is not life-threatening in people with normal immune status, yet because some individuals are unaware of ongoing infection, it may result in persistent itching and ultimately fissuring in the spaces between the toes. The most common complications of athlete's foot are subsequent toenail infection or bacterial skin infection (Field 2008). Unresolved infection can also spread to other parts of the body (such as the hands and the trunk) as well as to other individuals. Therefore, prompt diagnosis, treatment, and patient education are essential to reduce the spread and transmission of this type of infection. Oral treatment is used for chronic conditions or when topical treatment has failed; this is the subject of another Cochrane review (Bell-Syer 2012).
Strategies to reduce the risk of infection include ensuring that the feet and especially the spaces between the toes are kept dry; wearing socks made of natural fibres (cotton or wool); protecting feet while in public bathrooms, showers, swimming pools, and fitness centres; and wearing well-ventilated shoes whenever possible.
Description of the intervention
Topical interventions for the treatment of athlete's foot (interdigital tinea pedis) in the form of sprays, gels, creams, powders, or ointments.
How the intervention might work
Topical treatments for athlete's foot typically work by inhibiting fungal growth on the skin and can be categorised depending upon their specific mechanism of action. Most of these fungistatic treatments impede fungal growth by one of the following mechanisms:
a) inhibition of the formation of fungal membranes (e.g. itraconazole and terbinafine) (Joly 1992; Ryder 1985);
b) inhibition of microtubule synthesis (e.g. griseofulvin) (Borgers 1980); or
c) inhibition of protein synthesis (e.g. benzoxaboroles, which are transfer RNA (tRNA) synthetase inhibitors) (Baker 2006).
Fungicidal agents are believed to kill the fungus by destroying cell membrane integrity (tea tree oil) (Hammer 2003) or causing nucleic acid damage (ozonized oil) (Geweely 2006). Finally, some treatments, like undecylenic acid, which obstructs fatty acid biosynthesis, have both fungistatic and fungicidal activity (McLain 2000).
Why it is important to do this review
Numerous topical antifungal treatments have been investigated for the treatment of athlete's foot, including both over-the-counter and prescription medications. Moreover, new antifungal formulations are also under investigation for this condition. This review will assist people with athlete's foot, healthcare professionals, and healthcare decision-makers to revise the evidence on topical interventions for the treatment of interdigital tinea pedis.