Streptococcus salivarius K12
Oral probiotic strain · friendly bacteria native to healthy mouths
Streptococcus salivarius K12 is a friendly bacteria that naturally lives in healthy mouths. It crowds out the bacteria that cause bad breath, settles into the same surfaces where bad-breath bacteria grow, and produces compounds that slow their growth.* In the foundational study (Burton 2006), 85% of participants using K12 daily showed substantial reductions in the compounds that cause bad breath after 7 days.
Streptococcus salivarius K12, in plain language.
"Probiotic" covers many different bacteria. Even within a single species, individual strains can act very differently. Streptococcus salivarius K12 is one specific strain, selected and characterized for its support of oral health.
- The family it belongs to. S. salivarius is a group of friendly bacteria that naturally lives in healthy mouths.
- Where it settles in your mouth. K12 takes hold on your tongue, the back of your throat, and along the inside of your cheeks (Wescombe et al. 2009). Those are the same surfaces where the bacteria responsible for bad breath grow.
- Why this specific strain. Of the strains in this family, K12 has one of the strongest published research bases for daily oral support, going back to Burton et al. 2006.
What K12 does in your mouth.
K12 works in your mouth in two main ways:
- It crowds out the bacteria that cause bad breath.
The compounds responsible for bad breath come from specific bacteria living on your tongue. K12 settles into the same spots. With K12 there, the bad-breath bacteria have less room to grow. - It makes natural compounds that inhibit other strains.
S. salivarius K12 produces small molecules that slow the growth of less helpful bacteria. Your mouth ends up with a healthier balance.*
K12 does not stay forever. The studies show it lasts in your mouth for about one to three weeks at a time. That is why you take a Fenn Method oral probiotic mint every day. Fresh K12 keeps the population steady.
The evidence base.
K12 is one of the most-studied oral probiotic strains. In the foundational study (Burton et al. 2006), 85% of participants taking K12 daily showed substantial reductions in the compounds that cause bad breath after 7 days.
Other studies have looked at K12 for upper-respiratory health (Di Pierro 2016) and at how K12 settles into the mouth over time (Wescombe 2009).
K12 is well-studied within oral probiotics. Oral probiotic research overall is younger than gut probiotic research. We make no claim K12 cannot back. We do not say it treats or cures anything.
Why 1 billion CFU.
Each Fenn Method oral probiotic mint delivers 1 billion CFU of S. salivarius K12. "CFU" stands for colony-forming units. Think of it as "how many live bacteria are in there."
1 billion is the dose used in the K12 studies, and the level recommended for daily oral support.
That 1 billion is the minimum at the end of shelf life. Live probiotics lose count slowly over time, so we formulate with significant overage. In practice, every oral probiotic delivers a dose well above 1 billion CFU through expiration. The 1 billion floor is what we will stand behind on the label.
K12 is always paired with M18 in Fenn Method. K12 covers fresh breath. M18 supports healthy teeth and gums.* Together, they do more than either alone.
Questions about K12.
Q.01 How long does K12 stay in my mouth?
Q.02 Can I get K12 from yogurt or food?
Q.03 Is K12 safe for kids?
Q.04 What does "BLIS" stand for on some K12 product labels?
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