Linden (Tilia sp.) pollen allergy: Insights and challenges in the era of the allergy epidemic

Pollen allergies are an increasing global health concern. Linden pollen has traditionally been considered low-allergenic, leading to the widespread planting of linden trees in urban green spaces. However, this allergenic potential may be underestimated, resulting in linden pollen allergy being unrecognized. This review aims to identify and analyze the available literature on linden pollen allergy and provide, for the first time, a comprehensive synthesis of current knowledge. The reviewed studies offer evidence on the allergenic potential of linden pollen, its prevalence, associated clinical manifestations, and diagnostic approaches. However, significant knowledge gaps remain, including scarce epidemiological data, the absence of well-characterized linden pollen allergens, limited understanding of potential cross-reactivity, and undefined threshold exposure levels that may impact human health. The existing body of literature indicates that linden pollen has the potential to cause sensitization and allergic symptoms, thereby challenging its long-standing classification as low-allergenic pollen. The identified research gaps highlight the need for further interdisciplinary studies, spanning immunology, epidemiology, botany, and environmental science, to deepen our understanding of linden pollen allergenicity and its impact on human health.