Tea tree oil (Melaleuca alternifolia) has been traditionally used by indigenous Australians for its antimicrobial properties, and in recent decades, its use has extended to various skin conditions including athlete’s foot (tinea pedis). There is a moderate level of scientific evidence supporting its efficacy for this fungal infection.

Clinical studies have demonstrated that topical application of tea tree oil can reduce symptoms and, in some cases, eradicate the fungal organisms responsible for athlete’s foot. One randomized, double-blind trial (Carson et al., 1996, Australas J Dermatol) found that a 25% or 50% tea tree oil solution applied twice daily led to significant clinical improvement compared to placebo, with about 64% of participants in the 50% tea tree oil group achieving clinical cure versus 31% in the placebo group. Another trial (Satchell et al., 2002, J Family Practice) confirmed similar results, though complete mycological cure rates were lower, suggesting tea tree oil is more effective at relieving symptoms than fully eradicating the fungus.

Tea tree oil’s antifungal activity has also been demonstrated in vitro against dermatophytes such as Trichophyton rubrum and Trichophyton mentagrophytes, the primary pathogens in athlete's foot. Adverse effects are generally mild, including local irritation or dermatitis in sensitive individuals.

In summary, tea tree oil has both a traditional foundation and a moderate degree of scientific support for its topical use in treating athlete’s foot, though it may not be as effective as conventional antifungal drugs.