10-Undecenoic acid, also known as undecylenic acid, has a documented history of use as an antifungal agent, especially in the treatment of superficial fungal infections such as those caused by Candida species, the primary causative agent of thrush (oral candidiasis). The antifungal properties of undecylenic acid were first recognized in the mid-20th century, with both clinical use and scientific studies supporting its efficacy against Candida albicans. The mechanism involves disruption of the fungal cell membrane and inhibition of the morphogenic transition from yeast to hyphal form, which is critical for pathogenicity in Candida infections (Borecký et al., 2011).

In vitro studies have repeatedly demonstrated that undecylenic acid exhibits fungistatic and fungicidal activity against a range of Candida species. Its use is recognized in several over-the-counter topical preparations for skin and nail fungal infections. Regarding oral thrush, while undecylenic acid is effective in vitro and in animal models, clinical studies specific to its use in human oral candidiasis are limited. The available evidence supports its antifungal action, but there is less direct clinical trial data for oral administration or application in thrush compared to other antifungals like nystatin or fluconazole.

In summary, there is scientific basis for the antifungal effect of 10-undecenoic acid against the organisms responsible for thrush, but the clinical evidence for its effectiveness specifically for oral candidiasis is moderate, meriting a rating of 3 out of 5.