Pollen allergy and hay fever
All the information about pollen allergy and hay fever that is published on our website is provided by the Belgian Aerobiological Surveillance Network, which is managed by the Mycology & Aerobiology service from Sciensano.
The main allergenic pollens in Belgium
As soon as the first pollen grains appear again in the air, the dates of beginning and end of the season will be updated.
|Allergen||Beginning of the season||End of the season|
|Alder||02 February 2021||27 March 2021|
|Ash||20 February 2021||02 May 2021|
|Birch||24 March 2021||13 May 2021|
|Grasses||09 May 2021||28 July 2021|
|Hazel||02 February 2021||25 March 2021|
|Mugwort||28 July 2021|
|Oak||08 May 2021||04 June 2021|
The grass pollen
In Belgium, the grass pollen season usually last from May 15th to July 15th.
During this period, we evaluate the daily risk to develop hay fever symptoms by taking into account the measured airborne pollen concentrations (pollen grains/m³) and the weather forecast.
The risk index can be:
- Null: No grass pollen grain is expected in the air. Consecutive days with this index usually announce the end of the grass pollen season.
- Low: Low grass pollen concentrations in the air are expected but may be sufficient to cause allergic symptoms in highly susceptible individuals. The usual eviction measures are already recommended.
- High: High grass pollen concentrations in the air are expected. Many individuals allergic to this pollen are susceptible to feel symptoms. The usual eviction measures are recommended.
- Very high: Very high grass pollen concentrations in the air are expected. Most of the individuals allergic to this pollen are susceptible to feel symptoms. It is strongly recommended to avoid any activity outside.
We also measure the timing variations of the risk periods every year for the other main allergenic pollens.
For more information on the allergenic pollens, please visit the website www.airallergy.be of Sciensano.