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ACAAI > Patients & Public > Resources > Ask the Allergist

Has Climate Change Caused a Change in Pollen Levels?

Q.  I seem to be having an increasing amount of allergy problems earlier and earlier in the year and it seems to be getting worse for the past several years...I hear that each year allergies and pollen are getting worse.  Is that really true?  Is there a connnection to climate change?  

A.  Tree pollination appears to be starting earlier and lasting longer, as well as grass and weed pollination.  Ragweed especially appears to be increasing its northern reach into Canada, as there has been an increase in frost free days there! Pollen production and release indeed depend on the climate within which grasses, weeds and trees grow.  Factors include temperature, humidity, soil moisture, soil radiation and carbon dioxide (CO2) levels.  It does appear that across the continental United States (North America), that not only has the amount of pollen released increased with the various weather (meteorological) factors, but even the period of the year and the duration of pollen release appears to be changing as well (for the worse).