Ein Pollenkalender oder Pollenflugkalender stellt in tabellarischer Form die Art und das zeitliche Auftreten einer Pollenbelastung dar. engl.: One of the most common allergens is pollen . A hypersensitivity to pollen often results in seasonal allergic rhinitis (hayfever) or extrinsic asthma . The most common sources of pollen are weeds , grasses and trees and the manifestation of pollen-related hypersensitivity diseases are linked to higher amounts of certain pollen allergens in the atmosphere, depending on the season. Thus, these types of pollen allergy are often termed 'seasonal'.