Every spring, pine trees produce massive amounts of fine, yellow pollen that coats cars, sidewalks, outdoor furniture and windowsills.
This yellow dust — often called “the pollening” — causes a dusty mess but it’s rarely the cause of allergies, according to one North Carolina State University professor.
“Due to its large size and smooth surface, pine pollen is less likely to be inhaled deeply into the respiratory system,” said Robert Bardon, a professor of forestry and environmental resources in the College of Natural Resources.
Pine pollen particles are relatively large compared to other types of tree pollen, with some grains measuring roughly the thickness of human hair.
Despite their size, pine pollen grains are specially adapted for travel: each grain has two air sacs that increase buoyancy, allowing them to be carried long distances by the wind and even float on water.
But their relatively large size affects how they interact with the respiratory system. When inhaled, they are less likely to penetrate deeply into the lungs and are more often trapped in the nose and throat.
The smooth surface of pine pollen further reduces its ability to adhere to the walls of the upper airways, potentially decreasing its overall allergenic impact.
“I suspect that because pine and hardwood trees pollinate simultaneously, people often mistake visible pine pollen for the less obvious hardwood pollen actually causing their allergies,” Bardon said.
In North Carolina, tree pollen season typically spans from February to May. Pine trees usually release their pollen between March and April, which coincides with the pollen release from hardwood trees such as oaks and hickories.
Hardwood pollen is microscopic, which allows it to be inhaled more easily and to travel deeper into the respiratory tract, reaching areas that larger pollen typically cannot.
The rough surface of hardwood pollen can irritate the respiratory system, causing discomfort in the nose, throat and airways.
While pine pollen is generally considered less allergenic, it can still cause reactions in some people, especially those with sensitivities to other types of pollen or allergens.
A reaction to pine pollen can cause symptoms similar to hay fever, including coughing, sneezing, a runny nose and itchy eyes. In some cases, it may exacerbate asthma.
Trees release pollen throughout the day, peaking in the mid-morning. Humidity and wind affect this, with warm, dry and windy days causing the highest pollen levels.
Bardon suggests reducing pollen exposure by scheduling outdoor activities later in the day and evening when levels are lower.
Since pollen easily clings to surfaces like clothing, it’s helpful to change clothes and shower upon entering the home.
Additionally, regularly bathing pets that spend time outdoors can reduce the amount of pollen brought inside.
