A 2016 clinical study compared the efficacy of tea tree oil (TTO) with clotrimazole (a conventional antifungal drug) and “conservative management” (just washing) in the treatment of oral fungal infection.
36 otherwise healthy individuals of both sexes aged 20–60 years were enrolled in this interventional, observational, and comparative study. Tea Tree oil was found to be more efficient than either of the other interventions. Results for all three groups were compared on a percentage basis.
While allopatic antifungal agents are effective in the treatment of oral fungal infection, they present several major negative effects that cannot be overlooked (potential toxicity and resistance by fungal microorganisms).
The study concluded that TTO, being a natural product, is a better nontoxic modality compared to clotrimazole, in the treatment of oral fungal infection and has a promising future for its potential application in oral health products. The full text of the study can be found here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4738066/
There are a few issues with this report: it is not clear what dilution was used; TTO was used in water without any dispersant; and the composition of the oil is not stated. However, none of these invalidate the findings.