Recommendations for allergy-friendly urban planting in the context of climate change

Climate change is altering temperature patterns and pollen exposure, particularly in cities. Rising summer temperatures are reducing the well-being of urban populations: however, this impact can be partially reduced by suitable planting. Primarily, the issue is that exposure to pollen leads to sensitization and allergic symptoms more frequently in cities than in rural areas. Also, individuals with pollen allergies, especially those reactive to tree (hazelnut, alder, birch, ash) and grass pollen, experience more severe symptoms in cities due to the interaction of pollen with air pollutants. To counteract this trend, urban planting should prioritize nonallergenic, or low-allergenic plant species. Here we present a table categorizing tree species based on their allergic potential: (a) species that should not be planted under any circumstances, (b) species that should be avoided but can be planted with caution, (c) species currently regarded as allergy friendly. Adopting these recommendations should counteract a further increase in tree pollen exposure and, thus, the frequency of sensitization, especially in residential areas. This paper serves as an update of a previous recommendation for planting new trees in public spaces with allergy considerations, incorporating the 2022 GALK street tree list, which is maintained by the “Urban Trees Working Group”.