It happens to me every spring. The flowers start to bloom, and the days become warm and full of sunshine. All I want to do is be outside, sit in the grass with my dog and play my guitar, and then…

Bam. My eyes start to stream, and my voice sounds like someone duct taped my nostrils shut and gave my throat a sandpaper rubdown. I have to pause after every third word to sniff. Hay fever.

About 10 percent of Americans suffer from this annoying allergy, caused by ragweed pollen. For those of us with seasonal allergies, the responses become automatic. We take meds, we carry tissues, we square our jaws and push through. But one thing we don’t think to do is cut down our carbon footprint.

 
Although it’s fairly obvious that the clouds of smoke pouring out of our exhaust pipes and factories can’t be good for our respiratory health, it turns out that carbon dioxide emissions can actually make your allergies worse.
 
Dr. Paul Epstein of Harvard University discusses this unexpected connection in his book, “Changing Planet, Changing Health.” He writes about an experiment conducted by one of his students, measuring the effects of CO2 concentration on ragweed. The student grew plants in two chambers, one with a CO2 concentration of 350 parts per million (ppm), and the other with 700 ppm.
 
Not surprisingly, the plants in the chamber with more CO2 grew faster, by about 10 percent. After all, plants need CO2 to survive the same way that humans need oxygen. What was surprising was that those plants also produced way more pollen, cranking out 61 percent more of the nose-clogging particles than the plants in the other chamber.
 
It turns out that this change in production was actually mild compared to some other studies. One, conducted by Lewis Ziska, grew identical ragweed plants on a rural organic farm and in an urban setting. The plants growing in the city, where CO2 concentrations can approach 600 ppm, produced ten times more pollen.
 
While a stuffy nose is not life threatening, allergens can also aggravate asthma, chronic bronchitis, and other lung diseases that are sometimes deadly. This is made even worse when the allergens combine with particle pollution in the air and are then carried deeper into the lung than they could go on their own.
 
CO2 concentration is rising fast. When Dr. Epstein and his student did their study in 2002, the global level was about 373 ppm. Today, it is approaching 394 ppm. By 2050, it’s projected to be 600 ppm.
 
So the next time you start to sniffle in the spring, before reaching for your Zyrtec or your Claritin, remember the little things you can do to cut down your carbon footprint. Turn off your lights, don’t let your car engine idle, ride your bike to work. And then we can all breathe a little easier.