Allergens and Pollen | Climate and Health | CDC

Pollen is an airborne allergen. Climate change may increase pollen concentrations and extend pollen seasons, heightening health effects for more people.

Pollen is an airborne allergen that can affect our health. Pollen grains are tiny “seeds” dispersed from flowering plants, trees, grass, and weeds. The amount and type of pollen in the air depends on the season and geographic region. Though pollen counts are typically higher during the warmer seasons, some plants pollinate year-round.

Climate change may cause shifts in precipitation, fewer frost days, warmer air temperatures, and increased atmospheric carbon dioxide (CO2). These changes can affect:

Pollen exposure can trigger various allergic reactions, including symptoms of hay fever. Hay fever, or allergic rhinitis, happens when allergens like pollen enter your body and your immune system wrongly sees them as threats. If you have allergic rhinitis, your body then responds to the allergen by releasing chemicals that can cause symptoms in the nose.

Allergic rhinitis symptoms vary seasonally or year-round, depending on the allergen, affecting up to 60 million people annually in the United States. Symptoms from allergic rhinitis include sneezing, runny nose, and congestion.

Pollen exposure can also trigger symptoms of allergic conjunctivitis. Allergic conjunctivitis is eye lining (conjunctiva) inflammation due to exposure to allergens like those in pollen. Up to 30% of the general population and 70% of allergic rhinitis patients experience allergic conjunctivitis. Symptoms from allergic conjunctivitis include red, watery, or itchy eyes.

Individuals with respiratory conditions like asthma may be more sensitive to pollen. Exposure to pollen is linked to asthma attacks and increased hospital admissions for respiratory issues. Higher pollen concentrations and longer pollen seasons can increase sensitivity to allergens, triggering asthma episodes and reducing productivity in work and school.

Extreme rainfall and rising temperatures also can contribute to indoor air quality problems. For instance, they can trigger indoor mold growth, worsening respiratory conditions for those with asthma or mold allergies, challenging asthma control.