STOP: Indiscriminate Chlorhexidine Mouthwash Use Due to Breast Cancer Risk

Overview

Research shows that women with periodontal disease or tooth loss due to chronic gum infections are more than twice as likely to develop breast cancer compared to those with healthy gums.^[1][2] However, the following body of evidence highlights the need to reassess the widespread use of antimicrobial oral products like chlorhexidine (CHX) mouthwash, particularly in healthy individuals, as its use may carry unintended downstream risks. Emerging findings provide potential mechanistic insights into how CHX use might contribute to breast cancer and breast disease in a causal manner, warranting careful consideration of its routine application. Specifically:

Routine use of chlorhexidine (CHX) mouthwash may inadvertently contribute to breast cancer pathogenesis through a cascade of microbiome disruptions. At the core of this concern is the induction of oral microbial dysbiosis, characterized by the depletion of protective anaerobes and the overgrowth of Proteobacteria—an opportunistic phylum disproportionately enriched in breast tumor tissue. These microbial shifts mirror those observed in antibiotic exposure, implicating CHX in similar mechanisms of immune perturbation and systemic inflammation. Furthermore, mounting evidence points to a strong oral-gut microbial axis in breast cancer patients, suggesting that disturbances in the oral microbiome may have far-reaching effects beyond the oral cavity. Together, these findings highlight a biologically plausible, mechanistically supported risk pathway that challenges the continued, indiscriminate use of CHX in healthy individuals:

1. Microbial Dysbiosis and Breast Cancer

Studies show that CHX significantly reduces key pathogenic genera such as Porphyromonas and Fusobacterium in the oral cavity.^[3] In studies, these two pathogenic genera were found to be inversely correlated with the oral microbiome in breast cancer patients, leading researchers to speculate that these common oral pathogens may play a protective role. ^[4]

2. Promotion of Proteobacteria

CHX promotes the growth of Proteobacteria, a phylum that is the most enriched in breast tumor tissues.^[5]Proteobacteria blooms are also associated with antibiotic use, with some literature even proposing that antibiotics may potentially play a causal role in the condition.^[6] This microbial shift appears conducive to tumorigenesis, and this connection suggests that chlorhexidine CHX could create a microbiome signature linked to breast cancer.

3. Antibiotic Effects

CHX acts as an antibiotic, and its effects parallel findings that patients with breast cancer and non-malignant breast disease are more likely to have recently taken antibiotics in the past 30 days relative to controls.^[7][8] This highlights a potential role for microbial disruption in the etiology of these diseases, possibly mediated by systemic inflammation or immune dysregulation.

4. Oral-Fecal Microbiome Connection

The strong correlation between the oral and fecal microbiomes in breast cancer cases suggests that disruptions in the oral microbiome, such as those caused by CHX, might have downstream effects on gut microbiota.

Implications and Recommendations for Clinical Practice

Although a causal relationship has been suggested, the current evidence does not establish a causal relationship. Nonetheless, the consistent associations between CHX use and breast disease raise legitimate concerns about its potential role in disrupting microbial homeostasis and contributing to systemic pathologies. These findings justify urgent prospective research to clarify the long-term effects of CHX on microbial ecosystems and cancer risk. In the interim, routine use of CHX should be restricted to clearly defined clinical indications—such as acute gingivitis or periodontitis—rather than as a blanket approach to oral hygiene. Clinical emphasis should shift toward microbiome-preserving strategies, including the promotion of nitrate-rich diets, prebiotic toothpaste, and probiotic-oriented oral care. Finally, research-driven guidelines are needed to appropriately balance CHX’s short-term benefits against its potential systemic risks, particularly in populations vulnerable to breast pathology.

Research Feed

References

1. Oral health links breast cancer.. Saini R.. (J Pharm Bioallied Sci. Jul 3, 2011)
2. Periodontal disease may associate with breast cancer.. Söder B, Yakob M, Meurman JH, Andersson LC, Klinge B, Söder PÖ.. (Breast Cancer Res Treat. 2011)
3. Effects of chlorhexidine mouthwash on the oral microbiome.. Brookes ZLS, Belfield LA, Ashworth A, Casas-Agustench P, Raja M, Pollard AJ, Bescos R.. (J Dent. August 18 2021)
4. The oral microbiome and breast cancer and nonmalignant breast disease, and its relationship with the fecal microbiome in the Ghana Breast Health Study.. Wu Z, Byrd DA, Wan Y, Ansong D, Clegg-Lamptey JN, Wiafe-Addai B, Edusei L, Adjei E, Titiloye N, et al.. (Int J Cancer. Oct 15, 2022)
5. A comprehensive analysis of breast cancer microbiota and host gene expression.. Thompson KJ, Ingle JN, Tang X, Chia N, Jeraldo PR, Walther-Antonio MR, Kandimalla KK, Johnson S, Yao JZ, Harrington SC, Suman VJ, Wang L, Weinshilboum RL, Boughey JC, Kocher JP, Nelson H, Goetz MP, Kalari KR.. (PLoS One. Nov 30, 2017)
6. Antibiotic use in relation to the risk of breast cancer.. Velicer CM, Heckbert SR, Lampe JW, Potter JD, Robertson CA, Taplin SH.. (JAMA. 2004)
7. The oral microbiome and breast cancer and nonmalignant breast disease, and its relationship with the fecal microbiome in the Ghana Breast Health Study.. Wu Z, Byrd DA, Wan Y, Ansong D, Clegg-Lamptey JN, Wiafe-Addai B, Edusei L, Adjei E, Titiloye N, et al.. (Int J Cancer. Oct 15, 2022)
8. The Unknown Effect of Antibiotic-Induced Dysbiosis on the Gut Microbiota. Aleksandr Birg, Nathaniel L. Ritz, Henry C. Lin. (Microbiome and Metabolome in Diagnosis, Therapy, and other Strategic Applications, Academic Press, 2019.)