Pollen respiratory allergy: Is it really seasonal?

Abstract

Allergic rhinitis (AR) is a highly prevalent respiratory condition that carries a heavy burden and can have a significant impact on patient quality of life. AR is caused by seasonal or perennial exposure to outdoor pollens and molds as well as indoor allergic triggers. In this review article, we discuss the factors associated with the development of AR throughout the year and the fact that patients with AR need continuous treatment rather than seasonal treatment. Conventionally, AR has been mainly categorized into seasonal AR and perennial AR, but these classes do not seem to be well-adapted. Climate changes, temperature changes, and high carbon dioxide (CO₂) concentration affect the growth of plants and increase the length of pollen seasons and pollen allergenicity. Air pollution aggravates allergic sensitization symptoms in AR sensitized individuals. Due to increased air pollution and indefinite pollen seasons AR symptoms are present throughout the year. Patients with AR often need continuous treatment, which should be considered while making the strategy for treating allergic rhinitis sufferers. Management of AR involves avoiding the allergen, medications for symptomatic relief, anti-inflammatory therapies, and allergy immunotherapy. Although the first-generation H₁-antihistamines reduce AR symptoms, they cause sedation and impair cognitive functions; thus, second-generation antihistamines (ie, levocetirizine, loratadine, bilastine, fexofenadine) are preferred. The efficacy and safety of fexofenadine for the treatment of seasonal allergic rhinitis (SAR) symptoms have been demonstrated by numerous clinical studies, irrespective of the season and underlying allergen. In this review, we discuss the allergic rhinitis classification, the role of climate change, air pollution, and factors contributing to year-round symptoms in patients with AR and the need for continuous pharmacological treatment for management.

Keywords: Air pollution and allergy; Allergic rhinitis; Antihistaminic; Climatic change and allergy; Fexofenadine; Pollens.

Fig. 1

Heterogeneity of allergic rhinitis: Inducible mechanistic traits. Adapted from Gerth van Wijk and Smits, 2021 CD8, cluster of differentiation 8; NK, natural killer; Th2, Type 2 helper. Allergic rhinitis patients exhibit heterogeneous clinical traits, including monosenstization to polysensitization for various allergens combined with mild-to-persistent and/or moderate typical rhinitis complaints, together with comorbidities for asthma, such as airway hyperresponsiveness

Fig. 2

Pollen peaks in Europe. Darker boxes indicate the presence of pollen season