Most advice for bad breath tries to remove or suppress the bacteria that cause it. A new University of Washington trial is testing a different idea: instead of just killing the odor-causing microbes, can you replace them with a healthier mix borrowed from someone else’s mouth?

What the researchers are testing

In a news release dated June 3, 2026, the UW School of Dentistry described a first-of-its-kind clinical study that transplants oral bacteria from a healthy donor into a person with chronic halitosis. The thinking is that persistent bad breath often reflects an oral microbiome that has fallen “out of whack,” with anaerobic bacteria building up on the tongue and in the pockets between teeth and gums, where they break down organic matter and release the foul-smelling gases behind most bad breath.

“We know the oral microbiome can get out of whack. The question is, can you rebalance it? That is the hypothesis we’re proposing,” said Alvin Wee, a UW professor of restorative dentistry and a co-lead of the project. Research scientist and affiliate faculty member Alex Pozhitkov is the other co-lead.

How the procedure works

The trial recruits in pairs: a patient with chronic bad breath plus a healthy donor — ideally an intimate partner, family member, or trusted friend. According to the UW description, the donor first gets a full periodontal exam to confirm their microbiome is healthy. Bacteria are then collected from the donor and suspended in a small volume of saline.

The recipient undergoes a deep cleaning to strip out harmful bacteria and disrupt the biofilm, then rinses with the donor solution; a concentrated version is also applied at the gumline. About 90 days later, participants self-report whether their breath has improved. The team says it has completed four transplants so far, with preliminary evaluations underway.

The approach borrows from the logic of fecal microbiota transplants used in the gut: severely disrupt the established community, then introduce a healthy one to crowd out the troublemakers.

What the science says so far

The idea has some laboratory groundwork behind it. A 2024 feasibility study in BMC Microbiology proposed oral microbiota transplantation (OMT) as a way to restore microbial balance in intra-oral halitosis, and tested whether donor saliva flora could take hold using an oral-colonization model in Wistar rats. The authors framed it as an early feasibility analysis — a proof of concept — rather than evidence that the treatment works in people.

That is the key caveat for the UW trial too. This is early-stage research: a small number of transplants, outcomes that so far rely on participants’ own reports rather than published, peer-reviewed measurements, and no control group results to point to yet. “First-of-its-kind” also means unproven. Nothing here suggests an oral bacteria transplant is an available or recommended treatment today.

What it means for your breath

For now, the practical takeaway is unchanged. The most reliable tools against bad breath remain the basics — brushing, flossing, cleaning your tongue, and staying hydrated — with clinically studied oral probiotics as a possible add-on. If bad breath persists despite good hygiene, see a dentist to rule out gum disease or another underlying cause.

What’s genuinely interesting about this trial is the shift in thinking it represents: from scrubbing bacteria away toward deliberately reshaping the community that lives in your mouth. Whether transplanting a donor’s microbes can do that safely and lastingly is exactly what studies like this one will need to show.

Sources

This article is for general information and is not a substitute for professional dental or medical advice.