High season of grasses

At this stage, people sensitized to grass pollen should take all precautions. During sunny spells, the risk of allergy remains high.

In brief

Several grass species are in bloom.

On Thursday, 39 grass pollen grains per cubic metre of air were measured in Brussels. Airborne pollen amounts may increase during sunny spells. People suffering from hay fever should be vigilant and carefully follow their practitioner’s recommendations.

Large amounts of allergenic fungal spores of the genus Cladosporium are also present in the air. The spore concentration peaks of this mold are very temperature dependent.


Latest measure: 
Thursday, 2 July, 2020
20192020Mean 2010 - 2019threshold value22 Apr29 Apr06 May13 May20 May27 May03 Jun10 Jun17 Jun24 Jun01 Jul08 Jul15 Jul22 Jul020406080100120140grains / m³


Latest measure: 
Thursday, 2 July, 2020
20192020Mean 2010 - 2019threshold valueMayJunJulAugSepOctNov05000100001500020000250003000035000fungal spores / 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.