Tinea Cruris

Dermatophytes are fungi that invade and multiply within keratinized tissues (skin, hair, and nails) causing infection. Dermatophytes can be classified into three groups: Trichophyton (which causes infections on skin, hair, and nails), epidermophyton (which causes infections on skin and nails), and Microsporum (which causes infections on skin and hair). Based upon the affected site, these have been classified clinically into tinea capitis (head), tinea faciei (face), tinea barbae (beard), tinea corporis (body), tinea manus (hand), tinea cruris (groin), tinea pedis (foot), and tinea unguium (nail). Trichophyton is the most common isolate with tinea corporis and cruris. 

Occlusive footwear and tight fashioned clothes, has been linked to this infection. However, all people are not equally susceptible to fungal infection, even when they have similar risk factors. There is evidence of familial or genetic predispositions that could be mediated by specific defects in innate and adaptive immunity.  Impaired function of Th17 cells leading decreased production of interleukin-17 (IL-17), IL-22 (key cytokine in clearing mucocutaneous fungal infection) results in persistence of infection.

The predisposition factors of infection are underlying diseases such as diabetes mellitus, lymphomas, immunocompromised status, or Cushing's syndrome, older age, which could produce severe, widespread, or recalcitrant dermatophytosis. The areas of the body are more susceptible to the development of dermatophyte infections such as intertriginous areas (web spaces and groins) where excess sweating, maceration, and alkaline pH favor the growth of the fungus.

Treatment

Non-pharmacology

1. Wear loose-fitting garments made of cotton or synthetic materials designed to wick moisture away from the surface.
2. Areas likely to become infected should be dried completely before being covered with clothes. 
3. Avoid walking barefoot and sharing garments.

Pharmacology

A meta-analysis by Rotta et al.(2013) shows topical antifungals for the outcome of fungal cure showed butenafine and terbinafine each to be superior to clotrimazole, oxiconazole, and sertaconazole; terbinafine to be superior to ciclopirox, and naftifine to be superior to oxiconazole.

Cochrane review by El-Gohary, M. et al. (2014), on the topical antifungal treatments for tinea cruris and tinea corporis suggests that the individual treatments with terbinafine and naftifine are effective with few adverse effects. Other topical antifungals like azoles treatments are also effective in terms of clinical and mycological cure rates. Regarding combinations therapy of topical steroids and antifungals though there is no standard guideline. Topical antifungal are usually given once or twice daily for 2–4 weeks. 

Reference

El-Gohary, M. et al., 2014,' Topical antifungal treatments for tinea cruris and tinea corporis', Cochrane Database Syst Rev., vol. 8. 

Rotta, I. et al., 2013,'Efficacy of topical antifungals in the treatment of dermatophytosis: A mixed-treatment comparison meta-analysis involving 14 treatments', JAMA Dermatol., vol. 149, no.-, pp. 341–9. 

Sahoo, A. K. & Mahajan, R., 2016,'Management of tinea corporis, tinea cruris, and tinea pedis: A comprehensive review', Indian Dermatol Online J., vol. 7, no. 2, pp. 77–86.