Every summer, up to 1 in 5 people in Britain are affected by hay fever. Also known as seasonal allergic rhinitis, hay fever is caused by an allergy to pollen and fungal spores. The allergy typically occurs in the mucous membranes of the nasal passages and eyes, explaining the occurrence of the symptoms described below such as sneezing, itchy eyes and a blocked or runny nose.
Pollen affects a hay fever sufferer because their body’s immune system over-reacts to it, as if it were a toxic substance. The symptoms of hay fever usually start to occur when the pollen count, the number of pollen grains per cubic metre of air, exceeds 50. As a result, the weather can affect how severely a sufferer experiences symptoms – sun can raise the pollen count, wind can spread pollen and rain can lower the count.