What time of year do symptoms occur?
The most common allergen to cause hay fever is grass pollen, which peaks from around May to July every year in the UK.
However, pollen from shrubs, trees and weeds can also trigger hay fever.
For tree pollen, key times are February to June, while for weeds it’s June to September.
Some people develop a reaction to mould spores which are more likely to be present in September and October.
If you have an allergy to grass, trees and mould, you could have a very long hay fever season every year. Mould spores are present in the air all year round, but they are particularly prominent during harvest time, through autumn and in mild damp conditions.