Pollen to Probiotics: Seasonal Allergies and Your Gut

The gut microbiome plays a key role in how the body responds to seasonal allergens.

Supporting gut health may help reduce symptoms like sneezing and congestion.

Diet and probiotics are emerging tools in managing allergy-related inflammation.

The immune system and gut microbiota are connected, especially in the context of allergic diseases. Immune cells both shape and are shaped by the microbial populations in the gut, creating a dynamic, bidirectional relationship. While this interaction is complex and still being unraveled, growing evidence points to strong links between gut microbiota composition and disease risk—suggesting that modulation of the microbiome could be a strategy for preventing or managing immune-related conditions (Hoskinson et al., 2025).

Research into the rise of asthma and allergies points to reduced microbial exposure in early life as a key factor. Both human and animal studies suggest that insufficient colonization of the gut or respiratory tract by certain beneficial microbes can lead to improper immune development, making the body more prone to allergic reactions and infections (Lynch and Boushey, 2016). Scientists are now working to pinpoint the specific microbes that help train the immune system toward tolerance, with the goal of preventing conditions like childhood asthma before they begin.

Certain gut bacteria naturally produce histamine by converting the amino acid histidine through the enzyme histidine decarboxylase (HDC). This includes some probiotic strains such as Lactobacillus reuteri, L. casei, and L. delbrueckii subsp. bulgaricus. While these bacteria are part of the normal gut flora, their ability to generate biogenic amines like histamine may contribute to elevated histamine levels in the gut, potentially triggering or exacerbating histamine intolerance in sensitive individuals (Schink et al., 2018).

Interestingly, a recent clinical trial highlights the potential of the probiotic strain Bifidobacterium longum BB536 in easing symptoms of Japanese cedar pollinosis (JCPsis), a seasonal allergic condition. Those in the probiotic group experienced notable relief, with fewer people needing to discontinue due to severe symptoms and less reliance on allergy medication. Daily symptom tracking revealed significant reductions in runny nose, nasal congestion, and overall discomfort among those taking Bifidobacterium longum BB536. The probiotic also appeared to calm the immune system by suppressing the typical Th2-skewed allergic response, as seen in lower levels of allergy-related immune markers (Xiao et al., 2006).

Asthma and allergic rhinitis, two of the most common allergic diseases, have seen a sharp rise in recent decades. Research suggests that diet plays a significant role in shaping immune responses involved in these conditions. Nutrients such as vitamins A, D, and E, as well as zinc, selenium and dietary fiber, may help regulate the inflammatory pathways that drive asthma and rhinitis, partly through their effects on the gut microbiota. Emerging evidence also points to the potential of plant-based diets to reduce symptoms, though more clinical trials are needed to explore these links and inform dietary recommendations for prevention and management (Zhang, 2023).