Environmental allergies, such as hay fever, dust mite sensitivity, or mold-related reactions, are on the rise worldwide. 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, L. plantarum, B. longum, and Bacillus spp., may be a supportive option for individuals seeking occasional allergy relief by supporting immune tolerance and strengthening gut-epithelial defenses during allergy season. Clinical trials have indicated that combining these probiotic species 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
Understanding Environmental Allergies and the Immune System
Environmental allergies often result from an IgE-mediated Type 1 hypersensitivity response 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. With re-exposure, sensitized cells release histamine 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, characterized by elevated levels of cytokines, including interleukin-4 (IL-4), IL-5, and IL-13. These cytokines further stimulate IgE production and promote epithelial inflammation in mucosal tissues. Genetic predispositions, impaired epithelial barriers, or an imbalanced microbiota may promote imbalances in the immune response.
Crucially, the gut microbiome plays a key role in immune regulation. The gut-associated lymphoid tissue (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. A healthy and diverse gut microbiota may promote balanced immune tolerance by activating Tregs and suppressing pro-allergic Th2 responses. Conversely, gut dysbiosis, particularly with insufficient levels of Lactobacillus and Bifidobacterium spp., has been linked to increased allergic sensitivity and reduced microbial resistance.
Probiotic Strains for Supporting Balanced Immune Responses
Lactobacillus spp.
Lactobacillus strains 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 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.
One frequently cited strain, Lactobacillus paracasei (L. paracasei) has demonstrated efficacy in attenuating symptoms of AR, potentially improving overall QoL for individuals with occasional allergies. A systematic review and meta-analysis 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.
Furthermore, Lactobacillus plantarum (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 (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 species, including Bifidobacterium longum (B. longum), B. infantis, and B. breve, play a vital role in maintaining mucosal health 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, where they help ferment dietary fibers to produce SCFAs like acetate, lactate, and butyrate. These metabolites lower intestinal pH, 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 and promoting the secretion of IgA and the differentiation of Treg cells through the reduction of IL-4, IL-5, and IL-13, 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, including Bacillus coagulans (B. coagulans), B. clausii, and B. subtilis, offer potential benefits due to their heat stability, gastrointestinal resilience, and immunomodulatory 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.
Furthermore, probiotics containing Bacillus strains possess the intrinsic capacity to produce a diverse array of enzymes, secretory proteins, antimicrobial compounds, vitamins, and carotenoids, which may modulate cytokine release and attenuate pro-inflammatory cytokines 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
Probiotics and Children’s Gut Health
Spore-Based Probiotics: Guardians of Gut Health
The Latest on Allergic Response and Gut Microbial Composition
By Rachel B. Johnson, MS, CNS, LDN
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