Writing in International Immunopharmacology, researchers from Henan University of Science and Technology’s College of Food and Bioengineering and Wecare Probiotics Co., Ltd, highlighted that probiotics can alleviate allergic rhinitis by working via the gut-immune axis.
A total of 52 children aged six to 10 with allergic rhinitis were randomized to take two gummies containing W. coagulans BC99 or a placebo made of dextrin during the eight-week study.
Each probiotic gummy, provided by Wecare Probiotics, contained 10bn CFU of W. coagulans BC99.
The children were also required to follow dietary guidelines set by the World Health Organization during the trial, including limiting their total fat intake and meeting their natural dietary fiber requirement.
Two questionnaires, namely the Rhinitis Control Assessment Test (RCAT) and the Rhino-conjunctivitis Quality of Life Questionnaire (RQLQ), were given to assess changes before and post-intervention. Blood and stool samples were also taken to examine changes in inflammatory markers and at the gut microbiome level.
Better symptom control and quality of life
The probiotic group showed significant improvements in symptoms of allergic rhinitis and quality of life as compared to the placebo group, based on results from the two questionnaires.
For example, RCAT scores of the probiotic group had increased from 12.81 ±1.08 at baseline to 15.19 ± 2.06 post-intervention.
The RCAT measures six domains of allergic rhinitis, including nasal congestion, sneezing, watery/itchy eyes, sleep disturbance, and activity limitations. The higher the scores, the better the symptom control, with a score of at least 21 indicating suboptimal control. The total score is 30.
On the other hand, the RQLQ scores for the probiotic group fell from 61.69 ± 5.66 to 55.58 ±7.51.
The RQLQ evaluates seven domains, such as activity limitations, sleep disturbance, nasal symptoms, ocular symptoms, non-nasal/ocular symptoms, practical problems, and emotional function. The higher the scores, the greater the impairment.
In contrast, the placebo group showed minimal changes in both RCAT and RQLQ scores that were not statistically significant.
Changes in inflammatory markers
Alongside the symptom improvements was a significant reduction in inflammatory markers – such as TNF-α and IL-13 – in the probiotic group.
For instance, TNF-α fell from 32.9 to 26.39 pg/mL, and IL-13 levels decreased from 70.8 to 49.6 pg/mL in the probiotic group by the end of the trial.
A similar trend was also seen for IL-4, which usually plays an anti-inflammatory role but takes on a pro-inflammatory role in allergic responses. In this case, IL-4 levels in the probiotic group had reduced significantly from 47.2 to 28.6 pg/mL
In contrast, no significant differences in the inflammatory markers were seen in the placebo group before and after intervention.
“This indicates that W. coagulans BC99 can reduce inflammation levels in the body by regulating cytokines, thereby exerting a relieving effect on allergic rhinitis,” the researchers wrote.
Probiotics increased SCFAs
Another key finding was how BC99 supplementation had increased the abundance of short-chain fatty acids (SCFA)-producing bacteria, such as Bifidobacterium and Roseburia, while decreasing pro-inflammatory bacteria like Escherichia-Shigella and Collinsella at the same time.
By the end of the trial, beneficial SCFAs-producing bacteria, including Blautia, Gemmiger, and Agathobaculu,m were upregulated in the probiotic group as compared to the placebo group.
The most pronounced alteration was the increased abundance of Bifidobacterium, the researchers highlighted.
“The elevation of these beneficial bacteria may contribute to the alleviation of rhinitis symptoms in children with allergic rhinitis (AR) by enhancing gut barrier function, exerting anti-inflammatory effects, and promoting immune regulation,” the researchers wrote. “Collectively, these results indicate that BC99 successfully colonized the gut to a certain extent, increased the abundance of beneficial bacteria, reduced harmful genera, and ultimately modified the gut microbial composition in children with AR.”
Conversely, the placebo group showed higher abundances of Enterobacter and Escherichia-Shigella.
According to existing research, a greater amount of Enterobacter is typically correlated with intestinal inflammation and compromised gut barrier function.
This can potentially promote systemic inflammatory responses that exacerbate AR symptoms, the researchers wrote.
Pathways linked to SCFA biosynthesis
Further analysis found that BC99 supplementation has influenced key metabolic pathways, including enhanced PPAR signaling and purine metabolism, which are pathways linked to SCFAs biosynthesis.
Other pathways, such as biofilm formation-Vibrio cholerae and pyruvate, were significantly suppressed in the probiotic group.
“These findings indicate that BC99 alleviates AR through a dual modulation strategy: enhancing SCFAs-production-associated metabolic pathways while suppressing biofilm formation and pyruvate metabolism implicated in inflammatory pathogenesis,” the researchers wrote, but also cautioning that further verification at the molecular level is needed.
Source: International Immunopharmacology. doi: 10.1016/j.intimp.2025.115787. “Weizmannia coagulans BC99 alleviates pediatric allergic rhinitis via the gut microbiota-SCFAs- immunomodulatory axis: A randomized, double-blind, placebo-controlled trial.” Authors: Han Z et al.
