Breathe into your hand and give that air a sniff. If it makes your nose crinkle, you might have halitosis. Up to half of adults suffer from chronic bad breath, although estimates vary.

Now researchers at the University of Washington are testing a new treatment to cure chronic halitosis: oral bacterial transplants.

There are many causes of bad breath, but a vast majority of cases stem from bacteria living on the tongue or concealed in the deep, dark corners of gums and teeth. Every human mouth is filthy with bacteria, but not everyone has halitosis.

The UW team believes the discrepancy happens when a person’s oral microbiome gets out of whack, and the proportion of bacteria that produce the bad odors is too high.

The researchers are testing a treatment aimed at rebalancing the oral microbiome by applying a healthy mix of bacteria to the mouth. For each test, they’ve solicited two volunteers: someone with halitosis and someone without (ideally close friends or family members) who will provide healthy oral bacteria.

Before the transplant, the research team harvests healthy bacteria from the donor and gives the recipient’s teeth a deep cleaning. Then the healthy bacteria are delivered diluted in saline as a mouth rinse and squirted as a concentrate along the gumline. Participants report the results three months later.

This is the first time a bacterial transplant is being tested in people as a cure for halitosis, according to UW. But the idea of microbiome transplants has been around for a while. Fecal microbiota transplantation has become a recommended method of treating the intestinal infection caused by the bacteria C. diff. It’s being tested as a treatment for other intestinal diseases as well.

The UW researchers have completed transplants on an initial group of four people, and they’re currently evaluating the results.

They’re now seeking federal approval to test the therapy on a larger cohort, and expect testing to continue for up to two years.

The team will be seeking participants for the expanded trials.

In these All Science Snapshots, “All Science. No Fiction.” creator Jes Burns features the most interesting, wondrous and hopeful science coming out of the Pacific Northwest.

Find full episodes of “All Science. No Fiction.” here.

News Source : https://www.opb.org/article/2026/10/28/northwest-research-trial-tests-whethe-a-little-spit-swapping-can-solve-chronic-bad-breath/