Exploration of Allergic Rhinitis: Epidemiology, Predisposing Factors, Clinical Manifestations, Laboratory Characteristics, and Emerging Pathogenic Mechanisms

Allergic rhinitis (AR) is a widespread allergic condition, with its prevalence continuing to rise globally. This disease has a significant impact on patients' quality of life. Understanding the underlying pathophysiology is important to develop better-targeted therapies. For decades, the primary assumption has been that an allergy is caused by unbalanced and overactive immunological responses against allergens, driven mainly by activated T helper 2 (Th2) cells and due to aberrant T-regulatory cells. The more recent hypothesis that is gaining attention relies on the dysregulation of the epithelial barrier, which might result in allergen uptake as a primary defect in the pathogenesis of allergic reactions. The nasal epithelial barrier is considered a crucial first line of defense in the upper airway, as it protects the host's immune system from exposure to allergens. Thus, this review will discuss AR's epidemiology, predisposing factors, clinical manifestations, laboratory characteristics, and pathogenic mechanisms.