This study is designed as a randomized, double-blind, placebo-controlled human intervention trial targeting a population of university students with persistent allergic rhinitis (AR) symptoms. The primary objective is to evaluate the preventive effect and underlying mechanisms of yeast β-glucan on upper respiratory tract infections (URTIs), providing scientific evidence for the prophylactic use of prebiotics in high-risk populations.
All participants will be stratified by sex and body mass index (BMI), and then randomly assigned to either the yeast β-glucan group or the control group. During the 15-week study period-including a 1-week run-in phase, a 12-week intervention phase, and a 2-week follow-up phase-participants in the intervention group will take two yeast β-glucan capsules daily after meals, while the control group will take two placebo capsules with identical appearance, taste, and packaging.
Participants will be monitored daily for the occurrence of URTIs. In the event of an infection, the Wisconsin Upper Respiratory Symptom Survey (WURSS-24) will be used to assess symptom severity and duration. Medication use, including dosage, frequency, and timing, will also be recorded. Weekly follow-ups will assess changes in Total Nasal Symptom Score (TNSS), Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ), and adverse events. In addition, participants will undergo comprehensive follow-up assessments at Week 0 and Week 12, including TNSS and RQLQ questionnaires, a 3-day dietary intake survey, anthropometric measurements (e.g., height, weight, body fat percentage), and biological sample collection (blood, urine, and stool samples).
Aged between 18 and 35 years;
Meeting the symptom criteria for persistent allergic rhinitis (AR) as defined in the Chinese Guidelines for Diagnosis and Treatment of Allergic Rhinitis (2022, Revised Edition): (1) Symptoms: Two or more of the following-paroxysmal sneezing, watery rhinorrhea, nasal itching, and nasal congestion-lasting continuously or cumulatively for at least 1 hour per day; ocular symptoms such as tearing, itching, and redness may also be present; (2) Persistent AR: Symptoms occur on ≥4 days per week and persist for ≥4 consecutive weeks;
No use of probiotics, prebiotics, synbiotics, antihistamines, corticosteroids, or immunosuppressants within 1 month prior to screening;
Willing and able to maintain usual physical activity levels and dietary patterns during the study;
Use of antibiotics, osmotic laxatives (e.g., magnesium sulfate, lactulose), anthraquinone-containing agents (e.g., rhubarb, aloe, senna), or gastrointestinal motility-promoting drugs (e.g., metoclopramide, domperidone, cisapride) within 1 month prior to screening;
Diagnosed with non-allergic rhinitis (e.g., vasomotor rhinitis, infectious rhinitis, hormonal rhinitis, drug-induced rhinitis), or with nasal polyps, severe nasal septum deviation, cerebrospinal fluid rhinorrhea, or aspirin-exacerbated respiratory disease (AERD);
Patients with uncontrolled allergic comorbidities, including sinusitis, otitis media, allergic asthma, or atopic dermatitis;
History of serious gastrointestinal diseases (e.g., severe diarrhea, inflammatory bowel disease), or gastrointestinal endoscopy within the past month;
Parallel
yeast β-glucan
Dietary supplementParticipants in the intervention group will take yeast β-glucan capsules daily. Each capsule contains 250 mg of yeast β-glucan, along with an appropriate amount of maltodextrin and silicon dioxide. All participants in the intervention group will take two capsules once daily, swallowed with warm water after meals.
placebo
Dietary supplementParticipants in the placebo group will take two placebo capsules once daily in the same manner. The placebo capsules are identical to the intervention capsules in form, taste, appearance, and packaging, but contain only maltodextrin and a small amount of silicon dioxide.
Incidence of Upper Respiratory Tract Infections (URTIs)
Wisconsin Upper Respiratory Symptom Survey (WURSS-24)
The WURSS-24 is a 24-item validated questionnaire designed to assess the severity and duration of symptoms during upper respiratory tract infections (URTIs), as well as the impact on daily quality of life. Each item is rated on a 0-7 scale, with 0 indicating no symptoms or no impact, and 7 indicating the most severe symptoms or greatest impact. Higher total scores indicate worse outcomes. The total score ranges from 0 to 168.
Total Nasal Symptom Score (TNSS)
A scoring system to evaluate the severity of four nasal symptoms: nasal itching, sneezing, rhinorrhea, and nasal congestion. Each symptom is rated on a scale of 0 to 3, with a total score ranging from 0 to 12. Higher scores indicate more severe symptoms.
Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ)
A validated 28-item questionnaire covering seven domains: daily activities, sleep, nasal symptoms, ocular symptoms, emotional impact, practical problems, and environmental exposure. Each item is scored from 0 to 6; higher scores indicate greater impairment. Changes from baseline to post-intervention scores are used to evaluate improvements in quality of life.
IFN-γ
A signature cytokine of Th1-type immune responses, IFN-γ plays a critical role in activating macrophages, enhancing antigen presentation, and promoting cellular immunity. Fasting plasma levels of IFN-γ are measured using high-sensitivity ELISA kits.
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