High season of grasses

At this stage, people sensitized to grass pollen should take all precautions. The risk of allergy is high.

In brief

Several grass species are in bloom.

On Thursday, 25 grass pollen grains/m³ of air were measured in Brussels. 

Changing weather conditions are expected for the coming days. Pollen amounts in the air may be high again during sunny spells. People suffering from hay fever should be vigilant and carefully follow their practitioner’s recommendations.


Latest measure: 
Thursday, 4 June, 2020
20192020Mean 2010 - 2019threshold value22 Apr29 Apr06 May13 May20 May27 May03 Jun10 Jun17 Jun24 Jun01 Jul08 Jul15 Jul22 Jul020406080100120140grains / m³

Good to know

  • Typical allergy symptoms such as runny nose, cough or shortness of breath (in case of asthma) can easily be mistaken for a cold, flu or coronavirus infection. However, fever and body aches should be given special attention as they might be caused by viral infection. It is recommended to call your general practitioner in case of doubt.


  • The standardized pollen detection technique allows retrospective measurement of the levels from samples taken the day before. Samples are analyzed manually during the working days by optical microscopy. The update frequency is daily for the Brussels station and weekly for the other stations.