Efficacy and safety of a particulate yeast β-glucan preparation in the treatment of seasonal allergic rhinitis (BETALL): a randomised placebo-controlled crossover trial protocol

BACKGROUND: Allergic rhinitis (AR) has been shown to be a significant global health burden. Despite the existence of pharmacological treatments, mainly antihistamines, nasal corticosteroids, and decongestants, many individuals with seasonal allergies turn to alternative herbal medicines and nutritional supplements for the management of symptoms. The primary objective of the current study is to evaluate the efficacy and safety of a 500 mg daily dose of a yeast β-glucan preparation (M-Gard®) on reducing the severity of nasal and ocular symptoms in a population with seasonal AR. METHODS: This randomised placebo-controlled crossover trial will evaluate the effect of 500 mg of a 14-day M-Gard® or placebo (microcrystalline cellulose) supplementation period on the relief of grass pollen-induced AR symptoms in 20 generally healthy adults (18-65 years) with a history of recurrent seasonal AR. Participants will consume M-Gard® or placebo during 14 days, starting 12 days before the antigen challenge and ending 2 days after. Each supplementation period will be separated by a 2-week washout period. Allergy symptoms will be assessed at baseline (day 0) and on days 12-14 using a visual analogue scale (VAS) rating AR symptom severity as primary outcome (nasal congestion, sneezing, itchy nose, runny nose and watery eyes) and validated questionnaires as secondary outcomes (Reflective Total Nasal Symptom Scores (rTNSS), Reflective Total Ocular Symptom Scores (rTOSS), Rhinitis Control Scoring System (RCSS), and Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ)). In addition, onset of relief, use of rescue medication, and adverse events will be monitored for up to 2 days after the grass allergen challenge. Peak nasal inspiratory flow (PNIF) and pathology markers (cytokines, histamine, tryptase, and allergen-specific IgE) will also be measured. All outcomes will be analysed as the change from baseline and between-group comparisons will be assessed using appropriate models. DISCUSSION: The study hypothesis is that M-Gard® supplementation will be more effective than placebo in reducing AR symptoms. This research will strengthen the evidence base supporting the use of M-Gard® as a supplement for the management of AR. TRIAL REGISTRATION: ClinicalTrials.gov NCT06907680. Registered on March 27, 2025.