There’s a bad breath gene, scientists say. They gave mice stinky breath to prove it.

Bad breath can have a whole slew of causes, ranging from the relatively bland (like the horseradish you just ate) to the life threatening (like liver disease).

But for some unlucky souls, bad breath — or, as it’s known medically, halitosis — has a more simple, primal, difficult to cure explanation: genetics.

Researchers at the University of California Davis have now identified a gene mutation they say could be a root cause for that kind of bad breath, according to a new study the researchers published on Dec. 18 in the journal Nature Genetics.

“It’s important to identify the cause of persistent halitosis, and differentiate that cause from relatively benign causes … and the more morbid causes such as liver cirrhosis,” said Professor Kent Lloyd, director of the Mouse Biology Program at UC Davis, which conducted the research.

About 3 percent of the population has chronic bad breath with no apparent cause.

Recent research carried out in the Netherlands at Radboud University, and with collaborators across Europe, discovered that sulfur-based compounds are common in the breath of those whose halitosis runs in the family, according to the UC Davis researchers.

One of those sulfurous compounds — methanethiol, which is produced during digestion — smells like boiled cabbage.

When the UC-Davis researchers analyzed halitosis sufferers, they noticed that they had mutations to their SELENBP1 gene, which creates a protein in the body that breaks down the foul-smelling methanethiol into other compounds. That discovery suggests the SELENBP1 gene “might possibly be keeping the breath methanethiol concentration low,” according to the study.

To test the hypothesis, researchers knocked the same gene out of DNA in lab mice. Sure enough, those genetically edited mice had much higher levels of the sulfurous, smelly compound methanethiol than they otherwise would have.

“While we didn’t put our noses up to the mice’s mouths, we did measure high amounts of some of these odor-forming chemicals in their blood, matching precisely what was found in the patients,” Lloyd said in a statement.

When that methanethiol-heavy blood reaches the lungs, it seeps into humans’ breath — and comes out our mouths in the form of not-so-pleasant cabbage breath, the researchers said.

Right now there’s no treatment for the kind of bad breath that’s passed down from your parents, the researcher said. But with more research into this gene and mutation, that could change, the authors added.

This story was originally published December 19, 2017 at 8:06 PM with the headline "There’s a bad breath gene, scientists say. They gave mice stinky breath to prove it.."