What probiotic strains have evidence for efficacy for hay fever?

There are many different probiotic supplements currently available. All of them contain different types and doses of probiotic bacteria. This study provides evidence that the particular combination and dosage of three probiotics (Lactobacillus gasseri KS-13, Bifidobacterium bifidum G9-1, and Bifidobacterium longum MM-2) can improve the quality of life of people with hay fever. Previous studies studies have found that other species and strains of probiotic bacteria improve the symptoms of seasonal allergies in adults, including Bifidobacterium lactis NCC2818^[1], Bifidobacterium longum BB536^[2], Lactobacillus paracasei LP-33^[3], Lactobacillus GG^[4], and Lactobacillus gasseri TMC0356^[4]. This evidence indicates that a range of different probiotic bacteria are likely to be of benefit in seasonal allergies and that one particular probiotic supplement is not necessarily more effective than another. However, the benefit of probiotics for seasonal allergies was relatively small in all studies.