Streptococcus salivarius is a naturally occurring, commensal bacterium commonly found in the human oral cavity, including the pharynx and tonsillar crypts. There is a growing body of scientific evidence supporting its use for upper respiratory tract health, including the tonsils. Specifically, the S. salivarius K12 strain has been studied for its ability to inhibit the growth of pathogenic bacteria associated with tonsillitis and other throat infections, such as Streptococcus pyogenes, due to its production of bacteriocins like salivaricin A2 and B. Several placebo-controlled clinical trials have demonstrated that supplementation with S. salivarius K12 may reduce the incidence and recurrence of streptococcal pharyngitis and tonsillitis, particularly in children with recurrent infections.

While the majority of evidence centers on prevention of throat and pharyngeal infections, the tonsils are directly involved in these conditions, and the studies frequently assess tonsillar health as an endpoint. However, most trials are of small to moderate size, and the long-term impact on tonsillar immune function remains under investigation. Overall, there is moderate scientific validation for the use of S. salivarius in supporting tonsillar and upper respiratory health, particularly as a preventive strategy against recurrent bacterial tonsillitis.