Burning Mouth Syndrome, the Oral Microbiome, and Lactic Acid Bacteria: A Comprehensive Review of Clinical Features, Microbial Dysbiosis, and Probiotic Therapeutic Potential

Background: Burning mouth syndrome (BMS) is a chronic orofacial pain disorder characterized by persistent intraoral burning recurring daily for at least 2 h over more than 3 months, without explanatory mucosal or laboratory findings. It affects 1.7–7.7% of the population, predominantly perimenopausal and postmenopausal women, and conventional pharmacotherapy offers only partial relief. Aim: This narrative review examines the associative and mechanistic evidence linking the oral microbiome to BMS and evaluates the rationale for lactic acid bacteria (LAB) as a candidate therapeutic strategy. Methods: PubMed/MEDLINE, Scopus, and Web of Science were searched for English-language literature on BMS, the oral microbiome, and probiotics, supplemented by mechanistic data from related conditions. Results: BMS patients may exhibit a compositionally distinct salivary microbiome, with reduced alpha diversity in psychiatric-comorbid subsets, though findings are heterogeneous. LAB, particularly Lacticaseibacillus paracasei, show antimicrobial and immunomodulatory properties relevant to oral homeostasis, but direct clinical evidence in BMS remains scarce and largely preclinical. Conclusions: Current evidence is predominantly cross-sectional and associative; the oral dysbiosis–BMS link and the therapeutic potential of LAB should be regarded as hypothesis-generating, warranting biomarker-anchored, strain-specific randomized trials.