In the United States, approximately 81 million people are affected by seasonal allergies, also known as hay fever.^1,2 Many individuals with asthma also experience seasonal allergies, as allergens such as pollen are common triggers for asthma attacks.^3,4 This article will explore the health impacts of seasonal allergies and asthma, as well as the various environmental factors contributing to these allergic diseases.

Seasonal Allergies 

Health impacts. The degree to which pollen affects humans is known as pollen allergenicity—increased pollen counts result in more severe symptoms for allergy sufferers.^5–10 Allergies represent a significant public health concern, with symptoms such as sinus congestion, runny nose, and itchy eyes accounting for more than 13 million visits to doctors’ offices annually.^11–13 

Environment. In certain cities, climate change can lead to extreme weather events—such as heavy rainfall and heat—which in turn can significantly affect pollen levels and prolong the allergic season.¹⁴ The literature indicates that climate change has several impacts on seasonal allergies. Warmer spring temperatures prompt some plants to begin producing pollen earlier, while warmer fall temperatures may extend the growing season for plants like ragweed. Overall, rising temperatures and elevated atmospheric carbon dioxide (CO₂) levels make the excess pollen even more allergenic.^15,12,3,16

Other factors, such as increased greenhouse gas levels and warmer temperatures, also impact pollen production, including the quantity and the duration of the season.^5,6,17–20 Researchers predict that pollen levels will keep rising as temperatures and greenhouse gas concentrations increase.^5,7,21

Asthma

Health impacts. Symptoms of allergic asthma include shortness of breath, chest tightness, wheezing, and coughing.²² The literature suggests that the early onset of spring and associated pollen releases are linked to a higher risk of asthma-related hospitalizations.^5–9 When pollen travels through the air and breaks down, particularly through high-humidity zones, it can easily enter the lower respiratory tract, triggering an asthma attack.^3,23 Researchers found that each 10-grain increase in grass pollen per cubic meter was associated with a significant rise in the average number of emergency department visits in the United States, Canada, Australia, and Spain.^5,14

While the link between seasonal allergies and pollen is well established,^3,24,25 some of the literature reports that the role of pollen in seasonal allergic asthma is not fully understood yet. However, some studies have reported that seasonal allergies likely elevate the risk of developing asthma.^3,26,27,24

Environment. Climate change, increased urbanization, and decreased biodiversity has played a part in allergic asthma,^3,28 in addition to airborne allergens and air pollutants which can increase the concentration of the various allergens, leading to more severe asthma allergic reactions.^3,29,30

The literature indicates that thunderstorms can increase the risk ratio of asthma attacks by 1.24.^5,31 Thunderstorms can trigger severe allergic pollen reactions as the heavy amounts of rain and moisture rupture the pollen grains, intensifying their allergenicity.^5,32,3,33 

Bottom Line

Seasonal allergies and asthma, both of which are linked to environmental factors such as climate change, pose a growing public health challenge. As pollen levels rise due to warmer temperatures and increased atmospheric CO₂, allergy sufferers continue to face more frequent and severe symptoms. The increasing prevalence of allergic asthma underscores the need for comprehensive strategies to manage these conditions.

As researchers continue to uncover the complex consequences of climate change, environmental health, and allergic diseases, it is crucial to implement strategies to mitigate climate change, improve urban planning, and enhance public awareness. Overall, addressing the environmental impact of allergic diseases is not only essential for managing individual health and wellness but also for safeguarding public health for future generations. 

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