Pollen allergy season is firmly upon us this year, and some folks can’t seem to stop the sneezing and itching that accompanies the beautiful blooms of spring in Lancaster County. We talked to Dr. Christopher Hardy about what may be causing a perceived uptick in the severity of seasonal allergies and what you can do to combat it.   

But before we get there, we’ll need a brief science lesson on pollen and what role it plays in the plant kingdom.  

WHAT IS POLLEN & HOW DOES IT CAUSE ALLERGIES? 

Hardy, a professor of plant sciences at Millersville University, said plants use pollen to deliver sperm to the female part of a flower or cone of another plant. The transfer of pollen between plants is called pollination and, when achieved, a species-specific match between pollen coat proteins and the female plant will then induce the pollen to produce its sperm for successful fertilization and the formation of fruit and seed.  

Whereas many plants use bees, birds or even bats to carry their pollen, other plants release their pollen into the air instead and rely on the wind for pollination. Botanists call the latter such plants “anemophilous,” which is technical jargon for “wind-pollinated.” That yellowish dust on your car windshield each spring, for example, is pollen from wind-pollinated trees and, if it is on your windshield, you can rest assured it is also in your nose and eyes.  

Your seasonal pollen allergies are caused by the loose, airborne pollen of wind-pollinated plants that finds its way into your nasal passages and eyes, not the sticky pollen of animal-pollinated plants. The itchy, watery eyes, runny nose and excessive sneezing is your immune system’s over-reaction to the pollen coat proteins that it identifies as foreign, even though pollen presents no real threat. “There’s really nothing positive to come out of this hyper-allergic response by the body,” says Hardy, who suffers from seasonal allergies himself.  

CLIMATE CHANGE, LANDSCAPING & OTHER FACTORS AFFECTING POLLEN ALLERGIES 

And if you thought that your pollen allergies couldn’t get any worse, Hardy points to scientific research demonstrating that human-caused climate change has already worsened pollen seasons and will continue to further exacerbate health impacts in the foreseeable future. In brief, says Hardy, “Warmer temperatures and increasing atmospheric CO2 concentrations translate into more plant biomass, more flowers and, for wind-pollinated species, greater amounts of pollen released into the air.” These trends are happening everywhere, yet they are amplified in urban and suburban areas over rural areas because urban environments are warmer and have higher atmospheric CO2 levels than rural areas.  

Even in the face of these global and regional forces, however, there are more local factors that can affect the severity of your pollen allergy flare-ups, some of which you can control. Hardy says that, because the great majority of a wind-pollinated tree’s pollen is shed within 50 feet of the tree, the type of trees and other plants around your home or workplace can greatly influence the amount of pollen in the air around you (Fig 1).  

A 50-foot-tall pine in your backyard, for example, will drop millions of pollen grains into the air and surfaces around you. If tree pollen is a source of severe allergy flare-ups for you, then either avoid planting wind-pollinated trees in your yard or at least keep your windows closed during their peak pollen season, spanning late March through early May.  

You have less control over what is planted in your neighbors’ yards or around your place of work, however, and it just so happens that many of the trees popular with landscapers for aesthetic or maintenance reasons happen also to be wind-pollinated species that produce copious airborne pollen. Such species include pines and spruces, cedars and cypresses, birches, oaks and maples. Hardy says that where a plant falls on the allergen scale is never generally considered by landscapers, but he thinks it should be.  

Fig 1. The percent of total pollen shed from a pine and a cedar as a factor of distance from the tree. 

Hardy also recommends that if you have moderate to severe pollen allergies you should shower before bedtime during the pollen-allergy season in order to rinse the pollen from your face, hair and out of your eyes. He also recommends replacing your pillowcase and bedsheets with clean ones often during the pollen season. You’ll never exclude all pollen from the air around you, but the key, Hardy says, is keeping your pollen exposure below your “symptom threshold.” That’s the level above which you experience symptoms and below which you do not. Allergy medicines can offer even more protection by raising that threshold, yet they cannot completely eliminate the possibility of an allergy flare-up in the event of heavy exposures.  

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