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Tinea pedis


Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports

Tinea pedis is the most common form of cutaneous morphological pattern of superficial dermatophytosis in Western countries. Tinea pedis denotes infection of the feet, including toes, with a dermatophyte. It is colloquially known as athlete’s foot or foot ringworm. Tinea pedis affects quality of life – cosmetically due to disfiguring skin lesions causing social embarrassment, and symptomatically due to significant itching, leading to social and emotional distress. The role of fomites cannot be ignored in its propagation. Many studies have indicated the viability of fungal spores in house dust, which may be a factor in causing chronic and recurrent disease. An additional and important factor in disease causation is its geographical distribution – the disease being more prevalent in tropical regions due to the extremes of temperature and humidity. The worldwide disease prevalence is estimated to be in the range of 10%. Thus, safe and effective treatments are required to address this important public health concern. The disease often begins as a lateral toe cleft involvement that progresses to involve the rest of the foot, occlusive footwear being a major factor in spread. The disease is classified based on the character as well as distribution of lesions – vesicular (involving the soles of the feet), moccasin (involving the lateral aspect of the feet), and interdigital (involvement between the toes).

Management Strategy

For minor interdigital toenails’ involvement, topical preparations that include imidazoles and allylamines, twice daily for a duration of 2–4 weeks, are sufficient. For a more extensive infection, a severe inflammatory reaction, or infections complicated by a secondary bacterial infection, systemic treatments may be necessary. Condy compresses containing potassium permanganate, or aluminum chloride 20% solution, can help decrease the bacterial load and quell inflammation. Adjunctive agents such as topical urea may be valuable in tinea pedis that is dry or hyperkeratotic. Oral antifungal agents like itraconazole 200–400 mg/day for 2 weeks and terbinafine 250 mg/day for 2–4 weeks are currently commonly prescribed. The clinical efficacy and mycological cure rates for both itraconazole and terbinafine far exceeds both fluconazole and griseofulvin. Oral ketoconazole has fallen out of favor due to its propensity to cause hepatotoxicity. A longer duration of therapy may be required in patients with recurrent/chronic tinea pedis.

Control of community spread is an important epidemiological strategy, although it comes riddled with difficult practical implementations. Eradication of the dermatophyte from an individual affected toe cleft is a demanding and laborious process; according to some schools of thought, this may not be completely achievable. Frequent cleaning of community showers and religious places where barefoot walking is mandatory needs to be strictly implemented to diminish the community burden of tinea pedis infections. The use of open footwear and loose-fitting socks goes a long way in helping achieve clinical remissions in affected patients. Additionally, the use of topical therapies like ciclopirox olamine, ketoconazole, naftifine hydrochloride, sulconazole nitrate, and miconazole nitrate possessing additional antibacterial activity can aid patients with mixed infections. Erratic treatment in terms of dose and duration hinders both clinical as well as mycological cure.

Tinea pedis: the etiology and global epidemiology of a common fungal infection

Ilkit M, Durdu M. Crit Rev Microbiol 2015; 43: 374–88.

Trichophyton rubrum is the predominant causative agent. Interdigital tinea pedis is the most common form. Tinea pedis may induce a T-helper 2 response, which may accentuate atopy and thus contribute to refractory atopic dermatitis. The prevalence increases with age and it is rare in children. One study also demonstrated a higher prevalence of tinea pedis in comparison to tinea capitis in schoolchildren. Developed countries have a higher prevalence of infection. It is also the most common concomitant mycosis associated with toenail onychomycosis. No conclusive prevalence differences are observed in diabetics. An id reaction (autoeczematization) is a specific complication with the active vesicobullous variant but not with other subtypes.

Prevalence and epidemiology of tinea pedis and toenail onychomycosis and antifungal susceptibility of the causative agents in patients with type 2 diabetes in Turkey

Oz Y, Qoraan I, Oz A, et al. Int J Dermatol 2017; 56: 68–74.

A case control study with 600 diabetic patients and 152 control non-diabetic patients was performed. The development of tinea pedis was significantly related to increasing age and male gender. Trichophyton rubrum (53%) outnumbered other isolates in diabetics by a significant proportion. Non-dermatophytic fungal isolates (28%) were not uncommon.

Increased risk of tinea pedis and onychomycosis among swimming pool employees in Netanya Area, Israel

Shemer A, Gupta AK, Amichai B, et al. Mycopathologia 2016; 181: 851–6.

A prospective study was conducted on 169 employees in 21 swimming pool centers in Netanya in which 30% employees had only tinea pedis and 46% had a concomitant onychomycosis. Swimming pools remain an important source of fungal disease causation and spread among close contacts. T . mentagrophytes was the most common isolate seen in about 1 in 3 employees with tinea pedis.

Internal environment of footwear is a risk factor for tinea pedis

Sasagawa Y. J Dermatol 2019; 46: 940–6.

This was a cross-sectional, observational study involving 420 patients. The internal environment of the footwear associated with a high dew point (which is an index of content of degree of moisture in the environment) had a significantly higher incidence of tinea pedis and this was influenced by climate. It was also observed that a higher external temperature and humidity were associated with a higher incidence of tinea unguium compared with tinea pedis. Use of leather shoes and high heels had a stronger association with the disease compared with other footwear. Penetration and proliferation of both T. rubrum and T. mentagrophytes in the stratum corneum is seen at a critical level of 90% footwear humidity. Thus, the length of time a footwear is worn also becomes important in disease causation.

The current Indian epidemic of superficial dermatophytosis due to Trichophyton mentagrophytes – a molecular study

Nenoff P, Verma SB, Vasani R, et al. Mycoses 2019; 62: 336–56.

A prospective study of 201 Indian patients with dermatophytic infections involving various areas of the body. Fungal culture material was identified by genomic Sanger sequencing of the internal transcribed spacer (ITS) region and the translation elongation factor (TEF)-1α gene. Of the dermatophyte positive patients, 93% showed T. mentagrophytes and 7% showed T. rubrum . This was the first time that a switch from T. rubrum to T. mentagrophytes was demonstrated in India by molecular methods. The causative T. mentagrophytes ITS genotype VIII is now increasingly being identified in countries in Central Asia and Europe.

Specific Investigations

  • 1.

    Direct microscopic examination of wet mount using 10% potassium hydroxide after scraping the edges of lesion with a No.15 blade. The number of false positives with direct microscopy is high due to its inability to differentiate between dermatophytic and non-dermatophytic organisms. Skill of the technician is important to prevent false negative reports.

  • 2.

    Culture using Sabouraud dextrose agar with chloramphenicol alone and separately on Sabouraud dextrose agar with both chloramphenicol and cycloheximide, incubated at 37°C and 25°C, respectively, for up to 4–6 weeks. Culture is considered the gold standard but delayed results and poor sensitivity are a concern.

  • 3.

    Antifungal susceptibility testing – MIC 50 and MIC 90 are calculated. Testing is performed using microbroth dilution technique of Clinical and Laboratory Standards Institute guidelines (CLSI M38-A2). It is important for achieving good therapeutic outcomes and decreasing antifungal resistance in the community.

  • 4.

    Histopathological examination and periodic acid–Schiff staining of specimens to highlight the fungal hyphae. It takes about 2–3 days for preparation and is not specific for dermatophytes.

  • 5.

    Real-time polymerase chain reaction (RT-PCR) targeting the chitin synthase 1 gene (CHS1) of dermatophytes.

  • Molecular diagnostics are gaining popularity. They are rapid, more sensitive, more specific, and more cost-effective in diagnosing the fungal infection than the already available traditional methods.

  • 6.

    The Dermatophyte Test Strip detects dermatophytic antigen by immunochromatography using monoclonal antibodies that react with dermatophytes. It has a sensitivity of 84% and a specificity of 77%. It has a positive predictive value of 67% and negative predictive value of 90%. The positive and negative concordance rate is said to be about 80%.

Clinical application of a molecular assay for the detection of dermatophytosis and a novel non-invasive sampling technique

Gordon AK, McIver C, Kim M, et al. Pathology 2016; 48: 720–6.

Diagnosis of tinea pedis by the Dermatophyte Test Strip

Tsunemi Y, Takehara K, Miura Y, et al. Br J Dermatol 2015; 173(5): 1323–4.

First-Line Therapies

Topical therapy is recommended for most patients with tinea pedis. Gels and sprays are often used in interdigital involvement with maceration. Creams and ointments are used for the dry hyperkeratotic variant.

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