Lactobacillus casei is a probiotic strain that has been investigated for its potential role in supporting the restoration of healthy vaginal flora, particularly in cases of vaginitis. Scientific interest in L. casei and related Lactobacillus species stems from their ability to colonize mucosal surfaces and produce lactic acid, thereby lowering vaginal pH and inhibiting the growth of pathogenic bacteria and yeast, such as Candida albicans and Gardnerella vaginalis.

Most of the clinical studies on probiotics for vaginitis focus on Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14, but there is some evidence that L. casei strains may also be beneficial. A few small-scale trials and laboratory studies suggest that L. casei can adhere to vaginal epithelial cells and modulate the immune response, which may contribute to its protective effects. However, the overall body of evidence specific to L. casei is limited, with most studies either being preliminary, involving small numbers of participants, or using mixtures of Lactobacillus species where the effect of L. casei alone cannot be isolated.

In summary, the use of L. casei for vaginitis is supported by a plausible biological rationale and limited direct evidence. While it is not as well-established as other strains, it is sometimes included in probiotic formulations for vaginal health. The strength of clinical evidence remains modest, justifying a rating of 2 out of 5.