Sneezing, Coughing, Runny Nose: Unexpected Symptoms of Extreme Heat

Heat waves in the Southwest and Western U.S. have toppled temperature records, while 90.5 million people experienced dangerously high heat on Thursday. This extreme environment can lead to heat-related illnesses, such as heat stroke and heat exhaustion. While these conditions are traditionally associated with high temperatures, seasonal allergies can also flare up as temperatures rise.

Unusually hot days are a hallmark of human-driven climate change caused by an increase of carbon dioxide and other greenhouse gases in the Earth’s atmosphere from burning fossil fuels. In the presence of more carbon dioxide, allergenic plants, such as grass, oak and ragweed, produce more pollen, and warmer environments lengthen the time that plants grow and produce pollen. Between 1990 and 2018, pollen seasons became 20 days longer, and pollen concentrations increased by 21%. Air pollution from burning fossil fuels is also thought to exacerbate allergies by making the immune system more sensitive to some allergens. 

About one in four U.S. adults suffers from seasonal allergies, which are estimated to cause more than $3 billion in medical costs each year. Symptoms can include headache, sneezing, coughing, tiredness, stuffy nose and more.  Based on a study surveying workers, 55% of employees had allergy symptoms, which caused them to miss 3.57 days of work each year and be unproductive for 2.3 hours of each workday that they had symptoms. 

People with seasonal allergies may also have asthma, and more pollen can trigger asthma attacks. The burden of co-occurring asthma and allergies will likely fall on minorities in the U.S., who disproportionately face higher asthma cases, hospitalizations and deaths due to historical racial segregation and bias. Specifically, Black Americans are approximately five times more likely to visit the emergency room because of asthma and three times more likely to die from asthma, compared to white Americans. To add to this, Black Americans are more likely to live in areas with greater air pollution. 

Currently, areas known as “Allergy Capitals” — places that have high pollen counts and a higher number of allergy specialists to treat patients —that are located in the southern Midwest and Eastern regions of the U.S. are most impacted, but new areas may see worsening allergies as temperatures continue to rise and allergenic plants spread northward to areas that have fewer winter days below freezing. The rise of pollen due to climate change, now a regional issue, will become a national problem. 

People who suffer from allergies can avoid going outside on days with high pollen counts and make sure to change clothes and shower when they come inside to avoid carrying pollen to indoor locations. Over-the-counter medicines can also help alleviate symptoms. 

But these solutions don’t address the upstream problem of climate change. To ensure a healthier and safer environment, we must:

1.     Transition to clean energy. 

Pollen emissions and seasonal allergies are expected to intensify and worsen as carbon dioxide increases in the atmosphere. Stopping the burning of fossil fuels and switching to renewable energy will decrease the amount of carbon dioxide in the atmosphere. The use of renewable energy, such as offshore wind, as opposed to coal and oil, is estimated to lower the risk of heart attacks, asthma and hospitalizations. Decarbonization can improve air quality and benefit human health, can further lessen the amount of pollen that plants produce and stop the spread of allergenic plants to new areas.

2.     Ensure that care is accessible for all, especially the most vulnerable. 

Health care professionals and systems must be up-to-date on the needs of those impacted by climate change. This includes those who have severe allergy symptoms and are disproportionately handling climate change-related health consequences. Making health care centers more accessible for environmental justice communities and in geographic areas predicted to be hit the hardest during heat waves would lessen the negative health impacts during such periods. Heat action plans in Europe, the U.S. and Canada have been shown to reduce heat-related mortality and morbidity using several approaches, including disseminating information, implementing warning systems, and establishing plans to prevent or treat heat-related illnesses.   

3.     Remove other factors that aggravate allergies.

This includes not only addressing existing health concerns, such as asthma, among low-income and minority communities but also improving air quality. Air quality can be improved by mitigating the burning of fossil fuels, investing in public transit to reduce traffic emissions, creating more green spaces and improving bike infrastructure, among other approaches, to avoid intensified allergy symptoms. For instance, the Environmental Protection Agency (EPA) in the New England region is promoting the electrification of school buses to protect children from the consequences of being exposed to air pollution, such as hampered brain development and asthma. By eliminating a source of air pollution and a potential amplifier of asthma, allergies may be more manageable for community members.  

As heat waves become more frequent around the U.S., we must prepare for worsening allergies and asthma alongside other heat-related illnesses and increase awareness about the connections between climate change and worsening seasonal allergies. Earlier this month, the Biden-Harris administration outlined actionable steps to address extreme heat and improve climate preparedness, including guidelines to protect environmental justice communities. Policymakers must adapt and expand this framework to mitigate key drivers of climate change and, in turn, work to improve air quality in order to decrease heat-related illnesses, lessen the burden of seasonal allergies — and, ultimately, safeguard human health as temperatures continue to rise. 

Jinia Sarkar is a master’s of science student in the Department of Environmental Health at Harvard T.H. Chan School of Public Health and a student ambassador at the Center for Climate, Health, and the Global Environment. 

Leah Martin, MS, is an incoming doctoral student in the Department of Environmental Health at Harvard T.H. Chan School of Public Health and a student ambassador at the Center for Climate, Health, and the Global Environment. 

Dr. Kari Nadeau is chair of the Department of Environmental Health and John Rock Professor of Climate and Population Studies at Harvard T.H. Chan School of Public Health.