First evaluation of a symbiotic food supplement in an allergen exposure chamber in birch pollen allergic patients

Allergic rhinitis/rhinoconjunctivitis is the most common immune disease worldwide, but still largely underestimated, underdiagnosed, and undertreated. Dysbiosis and reduced microbial diversity is linked to the development of allergies, and the immunomodulatory effects of pro- and prebiotics might be used to counteract microbiome dysbiosis in allergy. Adequate symbiotic (multi-strain pro-, plus prebiotic) supplementation can be suggested as a complementary approach in the management of allergic rhinitis.The effects of the daily intake of a symbiotic food supplement (combination of Lactobacillus acidophilus NCFM and Bifidobacterium lactis BL-04 with Fructo-Oligosaccharides) for 4 months in birch pollen allergic rhinoconjunctivitis patients were investigated for the first time in an allergen exposure chamber (AEC) allowing standardised, reproducible pollen exposure before and after intake.Eligible patients were exposed to birch pollen (8000 pollen/m³ for 120 min) at the GA2LEN AEC, at baseline (V1) and final visit (V3) outside the season. The Total Symptom Score (TSS) and the scores for nose, eye, bronchial system, and others were evaluated every 10 min during exposure. Other secondary endpoints were the changes in well-being, Peak Nasal Inspiratory Flow (PNIF), lung function parameters, and safety. Co-primary endpoints were differences in Total Nasal Symptom Score (TNSS) and TSS after 120 min of exposure between both visits. Temporal evolution of symptom scores were analysed in an exploratory way using linear mixed effects models.27 patients (mean age 45 years, 15% male) completed the study. Both co-primary endpoints showed significant improvement after intake of the symbiotic. Median TNSS and TSS were decreased 50% and 80% at 120 min (adjusted p-value = 0.025 and p < 0.01 respectively).All four symptom scores and the personal well-being, improved to a clinically relevant extent over time, visible by a weaker increase in symptoms during 120 min of the final birch pollen exposure. No relevant differences were observed for PNIF, PEF, and spirometry. There were no airway obstructions or lung restrictions before and after both exposures. Late phase reactions after exposure were reduced after V3, documenting a better birch pollen tolerability of the patients. The safety and tolerability profile of the symbiotic food supplement was excellent, no adverse events (AEs) were observed.This first evaluation of a symbiotic food supplement in an AEC in rhinoconjunctivitis patients with or without asthma induced by birch pollen revealed a significant beneficial effect, harnessing significant improvements of symptoms and well-being while maintaining an excellent safety and tolerability profile.