# Pollen-Food Allergy Syndrome: Allergens, Clinical Insights, Diagnostic and Therapeutic Challenges
## 1 Introduction  
Allergic diseases have become a significant public health concern globally, affecting both developed and developing countries, with prevalence rates ranging from 10% to 30% in adults and exceeding 40% in children [1]. Among all allergic conditions, allergic rhinitis (AR) stands out as the most common, affecting a substantial portion of the global population and exemplifying the growing burden of allergies worldwide. Together with asthma and atopic eczema, AR forms the cornerstone of what has been aptly termed the \"allergy epidemic\", a term that captures the rising prevalence of allergic conditions worldwide. Respiratory allergies such as allergic rhinitis and asthma are triggered by various allergens such as tree and grass pollens from anemophilous plants, house dust mites, animal dander, and molds [2]. Respiratory allergies, especially to pollens and molds, often follow seasonal patterns, with symptoms typically coinciding with specific times of the year when certain allergens are most prevalent [3]. In the Northern hemisphere, for instance, tree pollen allergies are common in spring [4], grass pollen allergies peak in late spring and summer [5], and weed pollen, such as ragweed, becomes more prominent in late summer and fall [6]. These patterns are closely tied to the life cycles of plants and the release of airborne pollen, which varies regionally and climatically. Seasonal changes in temperature, humidity, and weather patterns, such as wind, can further influence the dispersion and concentration of allergens in the environment, contributing to the periodic nature of symptoms [7]. As a result, individuals with respiratory allergies often experience predictable flare-ups, which can serve as valuable indicators for preventive measures and treatment planning [8; 9; 10]. However, factors such as pollution and climate change have begun to blur these traditional seasonal boundaries. Rising temperatures, altered rainfall patterns, and increased levels of airborne pollutants are extending pollen seasons and intensifying allergen concentrations, leading to more unpredictable and prolonged allergy symptoms [11; 12; 13]. These changes challenge the conventional understanding of seasonal allergies, requiring adjustments in management strategies to address this evolving environmental landscape. Initially affecting wealthier populations [14], respiratory allergies have expanded to middle- and lower-income groups [15], reflecting broader environmental and lifestyle changes. Urbanization, reduced microbial exposure, and dietary shifts are among the factors contributing to this trend [16], particularly in middle-income countries experiencing rapid socioeconomic transitions. Therefore, AR prevalence demonstrates a wide range of variability across different continents, reflecting the influence of environmental, genetic, and lifestyle factors on its distribution. In Africa, the prevalence is relatively low, between 3.6% and 22.8%, possibly due to differences in exposure to allergens, climate, or underreporting in some regions [17]. In contrast, the Americas show the broadest range, from 3.5% to 54.5%, which could be attributed to diverse climates, urbanization levels, and healthcare access across North and South America [18; 19]. Asia and Europe also exhibit considerable variation, with prevalence rates ranging from 1.0% to 47.9% in Asia and 1.0% to 43.9% in Europe [20; 21; 22]. These variations may be linked to differences in pollen exposure, pollution levels, and awareness or diagnosis of AR. Interestingly, Oceania presents consistently higher prevalence rates, ranging from 19.2% to 47.5%, likely due to high allergen loads in the environment, such as grass pollens, combined with genetic predispositions in the population [23; 24]. Overall, these variations underscore the multifactorial nature of AR, shaped by both environmental exposures and socioeconomic conditions. This highlights the need for region-specific public health strategies to address the burden of AR effectively [25; 26].