There is some scientific evidence supporting the use of Lactobacillus (mixed strains) in the prevention of bladder infections, particularly recurrent urinary tract infections (UTIs), though the evidence is not strong or conclusive. Lactobacillus species are part of the normal vaginal and urinary microbiota and are thought to inhibit the growth of uropathogenic bacteria, such as Escherichia coli, by producing lactic acid and other antimicrobial substances, as well as by competing for adhesion sites on the mucosa.

Several clinical trials have investigated the effect of oral or intravaginal Lactobacillus supplementation for UTI prevention. Some studies have shown modest reductions in UTI recurrence, especially in women with a history of frequent infections. Notably, a 2008 Cochrane review concluded that while there is some evidence for benefit, it is not robust enough to recommend Lactobacillus as a routine treatment. More recent reviews and individual studies have echoed this, finding mixed results and highlighting the need for larger, well-designed trials.

Overall, Lactobacillus is not considered a primary or standard treatment for active bladder infection, but may offer some preventive benefit for recurrent UTIs. Its use is supported by plausible biological mechanisms and some clinical data, but the quality and consistency of the evidence is limited.