Lime juice and soap inhibit growth of dermatophytes in-vitro

Trichophytons are common causes of tinea pedis. There is a belief among rural communities in Sri Lanka that cleaning the toe webs with a piece of fresh lime fruit (Citrus acida) is helpful in preventing infections on the feet. Cassia alata ('Eth thora in Sinhala) leaf has also been claimed to have antifungal properties. We planned to evaluate the efficacy of fresh lime juice, Cassia alata (CA) leaf, lime juice with CA leaf and various soaps, in inhibiting dermatophyte growth in vitro. CA leaf pulp, pieces of soap (Lux, Pears Baby Soap, Lifebuoy, Sunlight etc.), CA leaf pulp with lime juice and lime alone were placed in small wells cut out on Sabouraud's agar plates with a topical spread of dermatophyte spores. Miconazole and econazole discs were used as positive controls. Fungal cultures were observed on day 3,5 and 7. There were definite zones of inhibition of fungal growth around lime juice, lime juice with CA leaf pulp, all the soaps tested and the positive controls. There was no inhibition around CA leaf pulp. pH of lime juice was 2.32 and that of Lux^R soap saturated solution was 10.28. We conclude that lime juice and soaps have antifungal properties against dermatophytes in vitro. It may be due to the fact that dermatophytes favour a pH of around 5.5 (normal body pH) for growth. This finding indicates that use of a piece of lime probably reduces the chances of colonization of dermatophytes on the toe webs, which has important public health implications. Cassia alata did not show any antifungal effect in this study.