Nasal administration of a probiotic assemblage in allergic rhinitis: A randomised placebo‐controlled crossover trial

BACKGROUND: Topical probiotics have been suggested as a treatment option for allergic rhinitis, as they may skew the immune response towards a beneficial type‐1 non‐allergic profile. So far observations in man have exclusively involved oral intake. The aim of this study was to examine whether a topical/nasal administration of a probiotic assemblage (PA) affects quality of life, symptoms and signs of allergic rhinitis in a nasal allergen challenge (NAC) model. METHODS: In a placebo‐controlled and crossover design, 24 patients with seasonal allergic rhinitis were randomised to topical/nasal administration with a PA of Lactobacillus rhamnosus SP1, Lactobacillus paracasei 101/37 and Lactococcus lactis L1A or placebo for 3 weeks. Participants and investigators were blind to treatment allocation. The last week of each treatment period was combined with a NAC series. Efficacy variables were “Mini‐Rhinoconjunctivitis Quality of Life Questionnaire” (Mini‐RQLQ), “Total Nasal Symptom Score” (TNSS), “Peak Nasal Inspiratory Flow” (PNIF) and “Fractional Exhaled Nitric Oxide” (FeNO). In addition, to assess whether or not the PA produced any pro‐inflammatory effect per se, soluble analytes were monitored in nasal lavage fluids. Finally, bacterial cultures, sampled using swabs from the middle nasal meatus, were assessed for the presence of the PA by MALDI‐TOF analysis. RESULTS: Administration of the PA did not produce any nasal symptoms (cf. placebo). An innate immune response was discerned within the PA run (cf. baseline), but no change in nasal lavage fluid levels of cytokines/mediators was observed cf. placebo except for IL‐17/IL‐17A (a minor increase in the PA run). Administration of the PA did neither affect Mini‐RQLQ, TNSS, PNIF nor FeNO. No evidence of persistent colonization was observed. CONCLUSIONS: Topical/nasal administration of a PA comprising Lactobacillus rhamnosus SP1, Lactobacillus paracasei 101/37 and Lactococcus lactis L1A, while likely evoking a minor innate immune response yet being safe, does not affect quality of life, symptoms or signs of allergic rhinitis. Trial registration: not registered.