Hayfever – what is it?
Hayfever is caused by an abnormal (or allergic) reaction of the body to pollen coming into contact with the nose, eyes or throat. The body’s immune system reacts to this usually ‘harmless’ substance as it thinks that, for some reason, it is ‘harmful’ – as if the body were being attacked by a potent virus.
As the immune system over-reacts, it releases large amounts of a chemical known as histamine. This causes itching, inflammation and irritation in the local tissue. Why the immune systems of people with hayfever over-react in this way is not known.
Pollen causing hayfever can come from grass, trees or flowers. In temperate climates such as in the UK and Ireland, pollen levels increase dramatically in spring as Nature comes to life.
As the weather warms up, grass, bushes, trees and other plants grow and develop in a coordinated fashion. In this way, pollen levels are highest during spring and early summer. In countries which are warm all year round, plants do not have these coordinated phases as they are able to grow and flower all year round. This explains why hayfever does not tend to be a problem in say, tropical countries.
Pollen levels in the UK are very much dependent on the weather. A week of dull rainy weather followed by a few days of warm sunshine, can drive pollen levels sky high – not good news for those with hayfever.
People suffering from hayfever may also be more sensitive to one form of pollen than another. This adds to variations in symptoms from month to month and also, from one area of the country to another.