Periodontitis: coriander mouthwash has no detectable effect on the salivary microbiome

Three mouthwashes compared over two weeks

The study, published on October 3, 2026, assigned participants to three groups: water, Coriandrum sativum essential oil mouthwash and 0.12% chlorhexidine. Participants rinsed twice a day for 14 days.

The researchers analyzed 54 saliva samples collected at the beginning and end of the trial. The groups included nine participants for water, eight for coriander and ten for chlorhexidine. Metagenomic sequencing enabled comparisons of the composition and diversity of microbial communities.

Coriander shows no detectable difference from water

For the primary outcome, which quantified changes in microbiome composition at the species level, no statistically detectable difference was observed between coriander and water. Analyses of microorganism diversity and abundance also showed no detectable difference.

This finding applies to the formulation and conditions tested. With only eight participants in the coriander group, it does not rule out modest effects or effects that vary from person to person. It demonstrates neither efficacy against periodontitis nor the product’s safety.

Chlorhexidine changes the microbiome more

Compared with water, chlorhexidine caused a greater change in microbial composition, a decrease in diversity measured by the Simpson index and extensive shifts across microbial groups.

However, changing the microbiome more does not mean improving oral health more. These measurements describe an ecological effect in saliva, not a clinical improvement in periodontitis.

Laboratory activity does not settle the clinical question

Before the trial, both agents had inhibited Porphyromonas gingivalis in the laboratory, with stronger activity for chlorhexidine. Cytotoxicity tests on fibroblasts had also guided the choice of coriander concentration. These preclinical findings do not prove efficacy or safety in patients.

To determine whether coriander has therapeutic value, the authors call for larger studies incorporating clinical, inflammatory and functional outcomes. The apparent preservation of the salivary microbiome is not, on its own, a reason to replace a treatment.

What we can take away

This trial distinguishes antibacterial activity in the laboratory from a measurable effect in patients. It provides no evidence of a clinical benefit from coriander mouthwash.