Lactobacillus paracasei has been investigated for its potential to support or treat rhinitis, particularly allergic rhinitis, based on its immunomodulatory properties. The bulk of evidence comes from modern clinical and preclinical studies rather than traditional use. Several randomized controlled trials and animal studies have evaluated L. paracasei supplementation for allergic rhinitis, focusing on its ability to modulate immune responses, particularly by shifting the balance from Th2 (allergy-promoting) to Th1 (less allergic) responses and by strengthening the mucosal barrier.

For instance, a notable clinical trial by Pelucchi et al. (2005, European Journal of Clinical Nutrition) found that a combination of L. paracasei with other probiotics reduced the severity of symptoms in adults with perennial allergic rhinitis. Additional studies confirm modest reductions in nasal symptoms and improvements in quality of life scores, but results are inconsistent and improvements are often moderate. Mechanistically, L. paracasei appears to decrease local IgE production and downregulate inflammatory cytokines.

While these results are promising, the overall quality and number of studies are still limited, and meta-analyses suggest only mild benefit, leading to a moderate but not robust evidence rating. Despite scientific interest, L. paracasei is not a replacement for conventional allergy treatments but may offer adjunctive benefit for some individuals with rhinitis.