The gravity and frequency of hay fever is increasing, which is partly due to global warming and pollution.
Patients suffer from hay fever several months a year.
In Belgium there are 3 hay fever periods:
The period of tree pollen, particularly hazel and birch, from January to April.
The period of grass pollen which occurs somewhat later, in May, June and early July.
The period of herbaceous pollen which occurs at the end of summer, but does not affect many people in Belgium.