Bifidobacterium lactis has received some scientific attention for its potential role in supporting or alleviating respiratory allergies, such as allergic rhinitis and asthma. Several clinical studies and animal models suggest that certain probiotic strains, including B. lactis, may help modulate immune responses associated with allergies by promoting a more balanced Th1/Th2 response and enhancing regulatory T cell function. For example, a few randomized controlled trials have investigated the effects of B. lactis (often in combination with other probiotics) on symptoms of allergic rhinitis, with some reporting mild improvements in symptom severity and quality of life, possibly due to reduced inflammatory cytokine production. However, the evidence remains limited, as results are sometimes inconsistent and many studies use multi-strain formulations, making it difficult to attribute benefits solely to B. lactis.

Animal studies have shown that B. lactis can reduce airway inflammation and IgE levels in allergy models, providing a mechanistic rationale for its use. Additionally, the strain's ability to strengthen gut barrier function may indirectly affect systemic immune responses, including those involved in respiratory allergies. Nevertheless, large-scale, high-quality human studies focusing specifically on B. lactis monotherapy are lacking. Thus, while there is a plausible scientific rationale and some supportive evidence, the overall strength of evidence is modest, and B. lactis should not be considered a primary or standalone therapy for respiratory allergies at this time.