Vulvovaginal candidiasis (VVC) is one of the most prevalent vaginal infectious diseases. The increasing incidence of drug-resistant Candida strains and the limited therapeutic options make the discovery of effective alternative therapies essential. Essential oils (EOs) have been suggested as a promising alternative and, interestingly, vapor-phase essential oils (VP-EOs) offer more advantages than direct application. This study therefore aims to evaluate the effect of oregano VP-EO (VP-OEO) on biofilms of antifungal-resistant vaginal isolates of Candida species (Candida albicans and Candida glabrata) and determine its mode of action. CFU, membrane integrity, and metabolic activity were assessed. In addition, a reconstituted vaginal epithelium was used to mimic vaginal conditions and evaluate the effect of VP-OEO on Candida species infection, analysed by DNA quantification, microscopy, and lactate dehydrogenase activity. The results revealed high antifungal activity of VP-OEO. There was a significant reduction (>4 log CFU) in Candida species biofilms. The results also show that VP-OEO’s mechanisms of action are related to membrane integrity and metabolic activity. The epithelium model confirms the effectiveness of VP-OEO. This study suggests that VP-EO can be considered a first step towards developing a complementary or alternative form of VVC treatment.

IMPORTANCE: This work presents a new approach to applying essential oils—exposure to the vapour phase—which can be considered a first step towards developing a complementary or alternative form of vulvovaginal candidiasis (VVC) treatment. VVC is a significant infection caused by Candida species and remains a common condition that affects millions of women every year. The great difficulty in treating VVC and the extremely limited effective therapeutic options make the development of alternative treatments crucial. In this context, this study aims to contribute to the development of effective, low-cost, and non-toxic strategies for the prevention and treatment of this infectious disease, based on natural products. Moreover, this new approach has several advantages for women, such as lower costs, easy access, an easier method of application, avoiding skin contact and, therefore, fewer negative impacts on women’s health.