If you are an allergy sufferer this time of the year, how surprised are you that A University of Iowa study finds tiny tree pollen particles can hang in the air for a long time after a rain shower, causing grief for allergy and asthma sufferers. U-I chemistry professor Betsy Stone is the study’s author who led a team into the rainy outdoors of Iowa City on 28 separate days early last year.

The research found the harder the rainfall, the longer the pollen fragments would remain suspended in the air. She notes there’s a difference between pollen and pollen fragments, as the smaller granules can make their way deep into the lungs and worsen a person’s allergic reactions.

The study was funded by the U.S. National Science Foundation and was published online in the journal Environmental Science & Technology Letters.