--- title: "The Microbiome-Allergy Connection: Probiotics in Clinical Practice" description: Probiotic strains such as Lactobacillus, Bifidobacterium, and Bacillus may support immune tolerance and ease seasonal or environmental allergy symptoms. image: https://www.casi.org/hubfs/casi/featured/july-8-the_microbiome-allergy-connection.jpeg --- An **educational publication of Designs for Health** [For Practitioners →](https://www.designsforhealth.com) [![casilogoresize2-2](https://www.casi.org/hubfs/casilogoresize2-2.png)](https://www.casi.org/) [Home](https://www.casi.org/) [Science Update](https://www.casi.org/articles/tag/science-update) [Research & Education](https://www.casi.org/articles/tag/research-education) [Archive](https://www.casi.org/articles/all) Search articles Search Research & Education # The Microbiome-Allergy Connection: Probiotics in Clinical Practice RJ Rachel B. Johnson, MS, CNS, LDN Jul 08, 2025 ![The Microbiome-Allergy Connection: Probiotics in Clinical Practice](https://www.casi.org/hs-fs/hubfs/casi/featured/july-8-the_microbiome-allergy-connection.jpeg?width=960) Environmental allergies, such as hay fever, dust mite sensitivity, or mold-related reactions, are [on the rise worldwide](https://pmc.ncbi.nlm.nih.gov/articles/PMC9841766/). For many people, seasonal sniffles and sneezing are not only bothersome but may also indicate deeper immune health imbalances. While prescription or OTC medications are often used for occasional allergies, there is increasing focus on the role that the gut microbiome and probiotic supplementation may play in supporting a healthy immune response and helping attenuate occasional environmental allergies. ## Clinical Implications Strain-specific probiotic supplementation, especially those containing [*L. paracasei*](https://www.nature.com/articles/ejcn201413), [*L. plantarum*, *B. longum*](https://pmc.ncbi.nlm.nih.gov/articles/PMC11496560/), and [*Bacillus*](https://pmc.ncbi.nlm.nih.gov/articles/PMC5554123/)spp., may be a supportive option for individuals seeking occasional allergy relief by [supporting immune tolerance and strengthening gut-epithelial defenses](https://pmc.ncbi.nlm.nih.gov/articles/PMC8064452/) during allergy season. Clinical trials have indicated that [combining these probiotic species](https://pmc.ncbi.nlm.nih.gov/articles/PMC11496560/) may promote a healthy immune response to allergens in both the adult and pediatric populations. Ongoing research is necessary to refine further strain selection, dosing protocols, and long-term benefits, but understanding the key takeaways below may help promote immune tolerance and overall quality of life (QoL) outcomes.  ## Key Takeaways - Probiotic supplementation may offer some relief for individuals with seasonal or environmental allergies, particularly when conventional therapies do not fully help. - [*Lactobacillus* and *Bifidobacterium* strains](https://pmc.ncbi.nlm.nih.gov/articles/PMC9161695/) have consistently demonstrated effectiveness in research in attenuating allergic rhinitis (AR) complaints, such as nasal congestion, sneezing, and itching. - Probiotic species, such as [*Lactobacillus*, *Bifidobacterium*](https://pmc.ncbi.nlm.nih.gov/articles/PMC9161695/), and [*Bacillus*](https://pmc.ncbi.nlm.nih.gov/articles/PMC5554123/) species (spp.), may help restore balance to the immune system, shifting from a [Th2-dominant, allergy-prone profile to a more tolerant regulatory T cells (Tregs)/Th1 orientation](https://pmc.ncbi.nlm.nih.gov/articles/PMC9161695/). - In children, [probiotic blends like NVP-1703](https://pmc.ncbi.nlm.nih.gov/articles/PMC11496560/) (*L. plantarum* and *B. longum*) have demonstrated clinical efficacy in reducing allergen complaints, supporting their role in pediatric care. - [*Bacillus* spp](https://pmc.ncbi.nlm.nih.gov/articles/PMC5554123/). are a shelf-stable, spore-based probiotic alternative that may promote a healthy gastrointestinal (GI) microbial balance, bowel regularity, digestive health, and foster a healthy inflammatory and immune response. ## Understanding Environmental Allergies and the Immune System Environmental allergies often result from an [IgE-mediated Type 1 hypersensitivity response](https://pmc.ncbi.nlm.nih.gov/articles/PMC9841766/) by the immune system. Usually, environmental antigens (also referred to as allergens) like pollen, pet dander, or mold spores are harmless. However, if these allergens are perceived as threats, the immune system initiates the production of IgE antibodies, which mainly [bind to mast cells and basophils](https://pmc.ncbi.nlm.nih.gov/articles/PMC9841766/). With re-exposure, [sensitized cells release histamine](https://onlinelibrary.wiley.com/doi/10.1111/pai.13854) and other inflammatory mediators, leading to classic allergy symptoms, including sneezing, itching, nasal congestion, and watery eyes. This process reflects a [Th2-dominant immune response](https://www.nature.com/articles/s41423-025-01261-2), characterized by [elevated levels of cytokines](https://onlinelibrary.wiley.com/doi/10.1111/pai.13854), including [interleukin-4 (IL-4), IL-5, and IL-13](https://pmc.ncbi.nlm.nih.gov/articles/pmid/36219943/). These cytokines further stimulate IgE production and promote epithelial inflammation in mucosal tissues. [Genetic predispositions, impaired epithelial barriers, or an imbalanced microbiota](https://www.nature.com/articles/s41423-025-01261-2) may promote imbalances in the immune response.  Crucially, the gut microbiome plays a key role in immune regulation. The [gut-associated lymphoid tissue](https://www.sciencedirect.com/science/article/pii/S1471490624000061) (GALT) houses a significant portion of the body’s immune cells and is influenced by microbial metabolites, particularly [short-chain fatty acids (SCFAs), such as butyrate](https://link.springer.com/article/10.1007/s11882-021-01020-z). A healthy and diverse gut microbiota may promote [balanced immune tolerance by activating Tregs and suppressing pro-allergic Th2 responses](https://pmc.ncbi.nlm.nih.gov/articles/PMC11496560/). Conversely, gut dysbiosis, particularly with [insufficient levels of *Lactobacillus* and *Bifidobacterium spp.*](https://pmc.ncbi.nlm.nih.gov/articles/PMC8064452/), has been linked to increased allergic sensitivity and reduced microbial resistance.  ## Probiotic Strains for Supporting Balanced Immune Responses ### *Lactobacillus* spp. [*Lactobacillus* strains](https://pmc.ncbi.nlm.nih.gov/articles/PMC8064452/) are among the most extensively researched probiotics within allergy studies and demonstrate significant immunomodulatory properties. These microbial species [may promote Treg and Th1 immune responses](https://pmc.ncbi.nlm.nih.gov/articles/PMC11496560/) by stimulating IL-10 and interferon-gamma (IFN-γ), while concurrently inhibiting allergy-associated cytokines such as [IL-4/IL-22, and IL-5/IL-22](https://pmc.ncbi.nlm.nih.gov/articles/PMC11496560/).  One frequently cited strain, [*Lactobacillus paracasei*](https://www.nature.com/articles/ejcn201413)(*L. paracasei*) has demonstrated [efficacy in attenuating symptoms of AR](https://pmc.ncbi.nlm.nih.gov/articles/PMC9161695/), potentially improving overall QoL for individuals with occasional allergies. A [systematic review and meta-analysis](https://pmc.ncbi.nlm.nih.gov/articles/PMC9161695/) of 28 studies examined the effects of probiotic supplementation on allergic diseases. The researchers found that varying microbial strains were effective in reducing AR symptoms by [promoting a healthy Th1/Th2 balance](https://pmc.ncbi.nlm.nih.gov/articles/PMC9161695/).  Furthermore, [*Lactobacillus plantarum*](https://pmc.ncbi.nlm.nih.gov/articles/PMC11496560/) *(L. plantarum)*, frequently used in conjunction with other probiotic species, has demonstrated benefits in reducing symptom severity in the pediatric population. In a [four-week, double-blind, randomized, placebo-controlled trial examining the effects of NVP-1703](https://pmc.ncbi.nlm.nih.gov/articles/PMC11496560/) (a combination of *Bifidobacterium longum* and *L. plantarum*) on nasal symptoms in children with AR (N = 68), NVP-1703 was able to significantly reduce allergic nasal symptoms by attenuating Th2 cytokine activity in nasal tissues. These results highlight the potential benefits of probiotic supplementation in supporting a healthy immune tolerance.  ### *Bifidobacterium* spp. [*Bifidobacterium*](https://pmc.ncbi.nlm.nih.gov/articles/PMC9161695/) species, including *Bifidobacterium longum* (*B. longum*), *B. infantis*, and *B. breve*, play a vital role in [maintaining mucosal health](https://pmc.ncbi.nlm.nih.gov/articles/PMC11687494/) by preserving epithelial integrity and supporting healthy immune responses. These beneficial bacteria are early colonizers of the [infant gut and remain key members of the adult microbiome](https://pmc.ncbi.nlm.nih.gov/articles/PMC11687494/), where they help ferment dietary fibers to produce [SCFAs like acetate, lactate, and butyrate](https://link.springer.com/article/10.1007/s11882-021-01020-z). These metabolites [lower intestinal pH](https://link.springer.com/article/10.1007/s11882-021-01020-z), creating a favorable environment for beneficial microbes while suppressing the growth of opportunistic or pathogenic bacteria, ultimately supporting a diverse and resilient gut microbial community.  *B. longum* has been shown to modulate immune function by [attenuating Th2 cytokine dominance](https://pmc.ncbi.nlm.nih.gov/articles/PMC9161695/) and [promoting the secretion of IgA and the differentiation of Treg cells](https://pmc.ncbi.nlm.nih.gov/articles/PMC8064452/) through the [reduction of IL-4, IL-5, and IL-13](https://pmc.ncbi.nlm.nih.gov/articles/PMC9841766/), as well as the promotion of anti-inflammatory mediators like IL-10. This immunomodulatory activity may contribute to restoring immune tolerance of harmless antigens, which is central in managing occasional allergic responses.  ### *Bacillus* spp. Although not as extensively studied as *Lactobacillus* and *Bifidobacterium*, [spore-forming *Bacillus* strains](https://pmc.ncbi.nlm.nih.gov/articles/PMC5554123/), including [*Bacillus coagulans*](https://www.sciencedirect.com/science/article/abs/pii/S175646461830553X) *(B. coagulans)*, *B. clausii*, and [*B. subtilis*](https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.1101144/full), offer potential benefits due to their [heat stability, gastrointestinal resilience, and immunomodulatory](https://www.sciencedirect.com/science/article/abs/pii/S175646461830553X) properties. Often found in fermented foods, *Bacillus* spp. are aerobic, gram-positive microbes that [promote a healthy gastrointestinal microbial balance, bowel regularity, digestive health, and a healthy inflammatory and immune response](https://pmc.ncbi.nlm.nih.gov/articles/PMC5554123/).  Furthermore, probiotics containing *Bacillus* strains possess the intrinsic capacity to [produce a diverse array of enzymes, secretory proteins, antimicrobial compounds, vitamins, and carotenoids](https://pmc.ncbi.nlm.nih.gov/articles/PMC5554123/), which may [modulate cytokine release and attenuate pro-inflammatory cytokines](https://pmc.ncbi.nlm.nih.gov/articles/PMC5554123/) such as IL-12, tumor necrosis factor-α (TNF-α), and IFN-γ.  ## Conclusion Emerging research suggests that probiotics may be a promising addition to help manage occasional environmental allergies. By regulating Tregs and Th2 inflammation in immune responses, strains such as *L. paracasei*, *L. plantarum*, *B. longum*, and *Bacillus* spp. may help reduce allergy complaints, including sneezing and congestion. Probiotic supplementation provides a well-tolerated, evidence-based approach to supporting immune balance and mucosal health.  **To learn more about probiotics and their role in overall health:**   [Clear Evidence: The Role of Spore-Based Probiotics in Healthy-Looking Skin](https://www.casi.org/articles/clear-evidence-role-of-spore-based-probiotics-in-healthy-looking-skin) [Probiotics and Children’s Gut Health](https://www.casi.org/articles/probiotics-and-childrens-gut-health) [Spore-Based Probiotics: Guardians of Gut Health](https://www.casi.org/articles/spore-based-probiotics-guardians-gut-health) [The Latest on Allergic Response and Gut Microbial Composition](https://www.casi.org/articles/latest-on-allergic-response-gut-microbial-composition)  On this page Share [LinkedIn](https://www.linkedin.com/shareArticle?mini=true&url=https%3A%2F%2Fwww.casi.org%2Farticles%2Fmicrobiome-allergy-connection-probiotics-in-clinical-practice) [X](https://twitter.com/intent/tweet?url=https%3A%2F%2Fwww.casi.org%2Farticles%2Fmicrobiome-allergy-connection-probiotics-in-clinical-practice&text=The+Microbiome-Allergy+Connection%3A+Probiotics+in+Clinical+Practice) [Email](mailto:?subject=The%20Microbiome-Allergy%20Connection%3A%20Probiotics%20in%20Clinical%20Practice&body=https%3A%2F%2Fwww.casi.org%2Farticles%2Fmicrobiome-allergy-connection-probiotics-in-clinical-practice) RJ ### Rachel B. Johnson, MS, CNS, LDN Clinical Application ## Clinical Considerations in Practice In clinical practice, practitioners considering the topics discussed above may also weigh nutrient form, delivery and formulation, alongside individual patient variability. ### Practitioner Formulation Example ![ProbioMed™ 50](https://cdn.sanity.io/images/lemtscrs/production-www/450a48dc081e8bd18faaee60a67355c751827c79-2000x1999.png?w=128&h=128&fit=max&auto=format) ProbioMed™ 50 Probiotic with 50 billion CFUs · Capsules [Explore Formulations →](https://www.designsforhealth.com/products/probiomed-50) ## Continue your research #### [Science Update A Case Report on Vitamin C Supplementation in a 67-Year-Old Male with Leukopenia Jul 21, 2026](https://www.casi.org/articles/a-case-report-on-vitamin-c-supplementation-in-a-67-year-old-male-with-leukopenia) #### [Research & Education How Akkermansia Supports GLP-1 Production and Metabolic Function May 27, 2026](https://www.casi.org/articles/akkermansia-supports-glp-1-production-metabolic-function) #### [Research & Education Overcoming the Anaerobic Barrier: A New Approach to Probiotic Manufacturing May 12, 2026](https://www.casi.org/articles/overcoming-the-anaerobic-barrier-a-new-approach-to-probiotic-manufacturing) #### [Science Update Integrative Management of Estrogen Dominance, Methylation Impairment, and Histamine Intolerance in Perimenopause: A Case Report Apr 23, 2026](https://www.casi.org/articles/integrative-management-of-estrogen-dominance-methylation-impairment-and-histamine-intolerance-in-perimenopause-a-case-report) ![casilogoresize2-2](https://www.casi.org/hubfs/casilogoresize2-2.png) An educational publication of [**Designs for Health**](https://www.designsforhealth.com). 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