Can LGG Chewables Reach the Nose and Ease Allergies?

Most probiotic allergy studies ask whether bacteria in the gut can influence the immune system elsewhere. A small 2025 trial asks a sharper question: what if the probiotic needs to reach the upper airway itself?

In a double-blind, placebo-controlled trial of 64 adults with grass-pollen allergic rhinoconjunctivitis, researchers tested a slow-release chewable containing Lacticaseibacillus rhamnosus GG (LGG). The formulation was meant to keep LGG in contact with the mouth and nasopharynx before it was swallowed, unlike a standard capsule that quickly passes into the stomach. The study used strain-specific quantitative PCR at nasal sampling sites to test whether LGG reached the upper respiratory tract. That delivery question—not a generic claim that "probiotics help allergies"—is the interesting part.

The caution is equally important: the available publication text does not report extractable numerical results for nasal colonization, IL-4 or IL-13, symptom scores, or statistical significance. The trial is a useful mechanistic lead, not evidence that an LGG chewable meaningfully relieves seasonal allergies.

Why route of delivery could matter

Seasonal allergic rhinoconjunctivitis begins where pollen lands: the nose and upper airway. In susceptible people, a type 2 immune response drives symptoms. IL-4 promotes IgE class switching in B cells and supports mast-cell and basophil sensitization. IL-13 contributes to mucus production, goblet-cell changes, and impaired epithelial barrier function. A local intervention that changed this cytokine environment could, in theory, affect the biology close to the site of allergen exposure.

That is different from the usual probiotic hypothesis. Most trials assume swallowed bacteria act through the gut-associated immune system and then produce systemic effects that reach distant tissues. The investigators behind the 2025 LGG chewable trial instead designed the tablet to prolong oronasal exposure and applied LGG-specific PCR to nasal samples. Direct molecular confirmation of upper-airway LGG after oral administration would answer a basic question earlier LGG allergy studies generally did not test: did the strain ever get to the relevant mucosa?

Biological plausibility is not proof of clinical benefit, but it is more than marketing copy. Lactobacilli, including Lacticaseibacillus species, occur at low abundance in the upper respiratory tract and have been reported as depleted in chronic rhinosinusitis. The same research group also reported that a different Lacticaseibacillus strain improved epithelial integrity in ex vivo tissue from chronic rhinosinusitis with nasal polyps. That supports the broad idea that some related bacteria can interact with airway tissue. It does not establish that LGG adheres to healthy or allergic human nasal epithelium, or that it changes symptoms.

What the LGG trial did—and what it cannot yet show

The Brussels study enrolled adults sensitized to grass pollen and followed them during pollen season, using local aerobiology data to track exposure. Sixty-one of the 64 randomized participants were included in the per-protocol analysis after three dropouts. Participants received either the slow-release LGG chewable or placebo. The study included nasal sampling, symptom measures such as total nasal symptom score and SNOT-22, and local cytokine endpoints.

Those are sensible endpoints for a route-of-delivery experiment. PCR evidence of nasal LGG would be a colonization endpoint; changes in IL-4 or IL-13 would be biomarker endpoints; total nasal symptom scores and medication use would matter more to a person trying to get through grass-pollen season without turning their desk into a tissue monument.

But the distinction matters. A biomarker shift would not prove symptom relief, and nasal detection would not prove durable colonization or local causation. More immediately, the quantitative outcome section is not available in the published text accessible here. We therefore cannot state the colonization rate, cytokine change, symptom difference, confidence intervals, or whether any between-group result reached statistical significance. Without those numbers, readers should treat the study as a test of an appealing hypothesis rather than a basis for treatment decisions.

The confounding problem

The trial also began with an important imbalance: 46.7% of participants in the probiotic group used intranasal corticosteroids at baseline, compared with 23.3% in the placebo group. Intranasal corticosteroids can suppress nasal type 2 inflammatory signaling and improve symptoms. If groups differ that much before treatment, later cytokine or symptom differences can reflect medication use as well as the chewable.

The per-protocol analysis adds another limitation. Excluding three randomized participants is not automatically fatal, but an intention-to-treat analysis better preserves the protection offered by randomization. Enrollment also occurred at different points in a single grass-pollen season, so participants encountered different pollen-load windows. With only 61 per-protocol participants, those differences can matter.

Finally, everyone chewed and swallowed the tablet. Even if LGG appears in nasal samples, the trial cannot separate a local upper-airway effect from the conventional gut–immune-axis pathway. A cleaner mechanistic test would need a comparison that isolates upper-airway delivery from gut exposure.

Probiotics for allergic rhinitis: a mixed record

The broader literature supports neither dismissal nor enthusiasm on autopilot. A 2022 systematic review and meta-analysis by Luo and colleagues found overall evidence that probiotics can improve allergic rhinitis outcomes, but studies varied substantially by strain, formulation, dose, participant characteristics, concurrent treatment, and outcome measurement. The pooled literature cannot tell us whether LGG works in a chewable designed for upper-airway contact.

LGG-specific results have been inconsistent. The 2025 paper describes an earlier placebo-controlled trial in 38 birch-pollen-sensitized teenagers and young adults in which standard oral LGG capsules did not significantly improve symptoms or medication use. Other positive LGG signals occurred in narrower settings, including combinations with sublingual immunotherapy, corticosteroids, or fermented milk products. Those results do not transfer automatically to adults taking a chewable alone during grass-pollen season.

Context dependence is a recurring feature of probiotic research. The 2025 Cochrane review of probiotics for prevention of allergic disease in infants likewise addresses a different population and a prevention question, but it reinforces the larger point: effects depend on strain, timing, formulation, and host factors. A strain name is not a clinical outcome.

The closest contradiction comes from the nose itself

Direct upper-airway delivery has already had a fair test—and it did not produce a clinical signal. In a randomized, placebo-controlled crossover allergen-challenge study, Mårtensson and colleagues gave a multi-strain probiotic assemblage by the nasal route to people with allergic rhinitis. The treatment was well tolerated but did not change allergic-rhinitis symptoms or clinical signs. The paper also discusses an earlier single-arm nasal lactic-acid-bacteria study that found no changes in IL-6, IL-8, MIG, IL-15, EGF, IP-10, or IL-1RA.

This does not settle the LGG chewable question. The strains differed, and nasal instillation is not the same exposure as slow dissolution in the mouth followed by possible nasopharyngeal deposition. Still, it is the most relevant counterweight to the theory that putting probiotics near the nose reliably changes allergy outcomes. It makes a null result plausible.

Evidence from other allergic diseases provides only indirect support. A 2025 systematic review of probiotic interventions for pediatric atopic dermatitis examined another type 2-skewed condition with overlapping immune pathways. Shared IL-4/IL-13 biology makes local immune modulation conceivable, but skin disease in children is not seasonal rhinitis in adults. It cannot validate nasal LGG.

What to do with an LGG chewable

If you already take LGG for a separate reason, choosing a slow-dissolve chewable rather than a swallowed capsule has a coherent theoretical advantage for upper-airway exposure. No evidence presented here identifies a safety disadvantage from that switch. It also does not show a clinically meaningful reduction in sneezing, congestion, itchy eyes, rescue medication use, or other allergy outcomes.

Verdict: The delivery hypothesis is worth watching because it tests whether location changes probiotic biology. It is not recommendation-grade evidence for treating seasonal allergic rhinitis.

For now, use therapies with established evidence for allergic rhinitis—intranasal corticosteroids, antihistamines, and, when appropriate, allergen immunotherapy—rather than substituting an LGG chewable. The next useful publication from this line of research should report the actual colonization frequency, symptom effect sizes, confidence intervals, medication-adjusted analyses, and intention-to-treat results. Until then, the most defensible claim is modest: where a probiotic lands may matter, but this trial has not yet shown how much it matters to patients.