The main drivers of allergies are predominantly non-climatic , but climate change strongly contributes to the spread of some allergenic plants, thus exacerbating existing allergies and causing new ones in people across Europe  . The prevalence of hay fever , for example, is between 4 and 30% among European adults . The invasive common ragweed  is a key species already causing major allergy in late summers , particularly in Hungary, Romania and parts of Russia . Across Europe, sensitisation to ragweed is expected to increase from 33 million people in 1986-2005 to 77 million people at 2°℃ GWL .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report