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Limited evidenceImmunity

Streptococcus Salivarius K12

An oral probiotic that colonises the throat and produces bacteriocins against Streptococcus pyogenes. Several trials report fewer sore throat and ear infection episodes, but almost all are small and poorly blinded.

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What the science says

  • Possible reduction in sore throat episodes Limited evidence

    A systematic review of K12 for treating or preventing sore throat found studies suggesting reduced episodes of streptococcal pharyngitis, while judging the trials small, largely non-blinded and at substantial risk of bias. The reviewers concluded that better trials are needed before recommending it.

  • Ear and oral cavity outcomes Limited evidence

    A systematic review of K12 in ear and oral health reported reductions in recurrent pharyngotonsillitis and acute otitis media across the available studies, again with methodological weaknesses throughout.

  • Paediatric prevention study Limited evidence

    An open-label study in three-year-old children reported fewer episodes of streptococcal pharyngotonsillitis, scarlet fever and acute otitis media over a 90-day treatment plus follow-up. The lack of blinding and placebo control limits what can be concluded.

Dosage & safety

Studied doseOne lozenge providing roughly 1 billion CFU per day, dissolved slowly in the mouth after brushing teeth at night. Studied courses typically ran 30–90 days.
SafetyWell tolerated in the trials. Live-organism probiotics should be avoided by people who are severely immunocompromised, have central venous catheters or are at risk of endocarditis. Lozenges are a choking hazard for very young children — paediatric trials used age-appropriate formulations.

How to take it

TimingAt night, last thing after brushing your teeth, with nothing to eat or drink afterwards.
With food?After food and brushing, so the strain has an undisturbed mouth to settle into.
Worth knowingLet it dissolve slowly — swallowing or chewing the lozenge sends the bacteria to the gut instead of the throat, which is not where they work.

Interactions

With medications

  • oral or systemic antibiotics

    Antibiotics kill the lozenge organism before it can colonise the mouth. take the lozenge at least 2 hours from an antibiotic dose, or start the course after finishing the antibiotic

  • antiseptic mouthwashes such as chlorhexidine

    They wipe out the strain you are trying to establish. separate by at least 2 hours, or skip the mouthwash while colonising

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does Streptococcus salivarius K12 prevent strep throat?

The evidence for S. salivarius K12 is limited: several studies report fewer streptococcal sore throat and ear infection episodes, but the trials are small, largely non-blinded and at substantial risk of bias. Reviewers concluded better trials are needed before recommending it.

How do I take the K12 probiotic lozenge?

Dissolve one K12 lozenge of roughly 1 billion CFU slowly in the mouth at night after brushing, with nothing to eat or drink afterwards. Chewing or swallowing it sends the bacteria to the gut instead of the throat; studied courses ran 30–90 days.

Can I take K12 with antibiotics or mouthwash?

Separate a K12 lozenge from antibiotic doses by at least 2 hours, or start after the antibiotic course, because antibiotics kill the strain. Antiseptic mouthwashes such as chlorhexidine also wipe it out, so separate them by at least 2 hours.

Is Streptococcus salivarius K12 safe for kids?

K12 was well tolerated in trials, but lozenges are a choking hazard for very young children and paediatric trials used age-appropriate formulations. Live probiotics like K12 should be avoided by people who are severely immunocompromised, have central venous catheters or are at risk of endocarditis.

Scientific references

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