Spring might have gotten off to a slow start this year, but that hasn’t dampened the effects of pollen. In fact, Dr. Clifford Bassett, founder and medical director at Allergy and Asthma Care of New York told weather.com he predicted “a very robust pollen explosion” this spring — and he wasn’t wrong.

According to the doctor, there are a number of reasons for the spring sniffles. “One is the rising long term increase in carbon dioxide and its effect on increased production of pollen,” he said.

“There’s a couple factors,” Dr. Clifford Bassett, founder and medical director at Allergy and Asthma Care of New York, told weather.com. “One is the rising long term increase in carbon dioxide and its effect on increased production of pollen,” another is what he calls “the priming effect,” and the last comes down to a battle of the sexes: pollen-producing male trees are dominating greenspace in many cities.

Read More: http://www.weather.com/health/pollen/news/2015-pollen-season