The cause of hay fever is an allergic reaction of the body to certain blossom, tree and grass pollens.
These substances (allergens) are falsely recognised by the body as "enemies”.

It forms antibodies with each renewed contact, which immediately causes an allergic inflammation reaction.
It is often accompanied by sneezing and itchy skin. The mucous membranes of the nose and eyes swell and build up added liquids. It can change stages which crosses over to complaints about bronchial mucous and can lead to allergic asthma.