Allergic rhinitis (AR), also known as nasal allergy, hay fever or seasonal allergic rhinitis, is an inflammatory condition of the nasal passages caused by the immune system's response to allergens in the air. Symptoms include runny or blocked nose, nasal itching, sneezing, and red, itchy, and watery eyes. These symptoms typically occur within minutes of exposure to allergens and can affect sleep, work productivity, and concentration during learning. Many patients with allergic rhinitis also suffer from conditions such as asthma, allergic conjunctivitis, or atopic dermatitis.Symptoms in the majority of patients tend to recur and persist over time. While medication can alleviate the symptoms, complete cure is challenging to achieve.

Probiotics are generally defined as microorganisms that, when ingested, provide beneficial effects to the host. They primarily consist of bacteria that produce lactic acid, including Lactobacilli, Bifidobacteria, and Saccharomyces boulardii. One known mechanism underlying allergic diseases is the overactivation of Th2 cells, leading to an imbalance in the Th1/Th2 ratio. Previous research has explored whether the use of probiotics can prevent allergic diseases. Numbers of studies indicate that probiotics have the ability to modulate the immune system by increasing anti-inflammatory cytokines such as IFN-γ, IL-10, and IL-12 to enhance Th1 cell activity. Simultaneously, they suppress pro-inflammatory cytokines like IL-4, IL-5, and IL-13, inhibiting excessive Th2 activation and restoring Th1/Th2 balance to improve symptoms.

Current evidence from clinical randomized controlled trials suggests that supplementation with probiotics during pregnancy and early infancy can prevent allergies or the development of more severe allergic conditions. However, regarding AR, current research has confirmed that probiotic consumption can improve the quality of life and the severity of nasal symptoms (measured by PRQLQ and TNSS) in AR patients. Nevertheless, the efficacy of regulating AR varies based on different strains or species of probiotics used.

This project aims to select probiotic strains that enhance the function of regulatory T cells (Treg cells), thereby promoting the secretion of Th1 cell cytokines IL-12 and IFN-γ to assist in achieving Th1/Th2 immune balance. This approach aims to reduce specific immunoglobulin E (IgE) levels and achieve an anti-inflammatory effect, thereby improving the regulation of allergic reactions within patients' bodies.

1. Inclusion criteria:

   1. Age between 6 and 65 years.
   2. Diagnosed with allergic rhinitis by a qualified physician.
   3. Score ≥ 7 on the Score for Allergic Rhinitis (SFAR).
   4. Willing to participate and has signed the informed consent form.

2. Exclusion criteria:

   1. History of drug allergy or use of medications with high sensitivity or contraindications (e.g., allergy to antibiotics or antipyretics).
   2. Patients with rhinitis symptoms caused by structural abnormalities such as a deviated nasal septum.
   3. Patients receiving oral corticosteroid therapy.
   4. Consumption of probiotic-related products within the past 1 month (including drops, tablets, capsules, powders, yogurt, or fermented milk containing live bacteria).
   5. Participation in other clinical studies within the past 1 month.
   6. Receipt of immunotherapy within the past 1 year.
   7. Presence of major illnesses (e.g., possession of a catastrophic illness certificate) or severe immune, hematological, or congenital disorders.
   8. Deemed unsuitable for participation by a physician.