Essential Oils and Plant-Derived Volatile Compounds in the Treatment of Oral Candidiasis: A Systematic Review of Randomized Controlled Trials in Denture Stomatitis

Background: Denture stomatitis, the most common form of oral candidiasis among denture wearers, remains highly prevalent, and antifungal resistance is an emerging concern. Essential oils and plant-derived volatile compounds show broad-spectrum antifungal activity in vitro, generating interest as complementary therapies. This review evaluated the clinical efficacy, mycological efficacy, and safety of these compounds versus conventional antifungals or placebo, based solely on randomized controlled trials (RCTs). Methods: Following PRISMA 2020 guidelines and PROSPERO registration (CRD420261473618), PubMed, Embase, Scopus, and Cochrane CENTRAL were searched on 20 July 2026 for English-language RCTs published up to 30 June 2026 and evaluating topical essential oils or volatile compounds against a conventional antifungal or placebo comparator in oral candidiasis. Two reviewers independently conducted screening, extraction and RoB 2 risk-of-bias assessment. Due to heterogeneity, findings were synthesized narratively. Results: Eight RCTs (347 participants), all in denture stomatitis patients, met inclusion criteria, evaluating oils from Zataria multiflora, Cinnamomum zeylanicum, Melaleuca alternifolia, Pelargonium graveolens, Satureja hortensis, Artemisia sieberi, and clove/cinnamon extracts. In active-comparator trials, no statistically significant differences in clinical outcomes were detected, but these trials were small and underpowered and none defined a non-inferiority margin; mycological efficacy varied, sometimes favoring nystatin or miconazole. Both placebo-controlled trials favored essential oil gels for clinical and mycological recovery. Adverse effects were inconsistently and mostly non-systematically reported; one trial reported vertigo, nausea and vomiting in the essential-oil group. Overall risk of bias was low in three trials and raised some concerns in five for both outcomes. Conclusions: The evidence for essential oils in denture stomatitis is preliminary and insufficient to support replacing conventional antifungal therapy; the findings cannot be extrapolated to other forms of oral candidiasis. Safety data are insufficient to draw firm conclusions. Standardized formulations and larger, well-designed RCTs with longer follow-up and safety assessment are needed.