The Surprising Link Between Light Pollution and Allergies

Every spring, Maya knows exactly what’s coming, and no amount of preparation helps. The unexpected sniffles, the perpetual itchy eyes, and the boxes of tissues that seem to disappear faster than she can buy them. Like most people, Maya always assumed her seasonal allergies would simply disappear as soon as summer hit. Lately though, her allergy season just doesn’t seem to stick to the usual timeline, and it turns out the reason behind her endless misery might be something entirely unexpected: city lights.

Most tend to think of light pollution as a problem only when it causes hazy night skies and diminishes our view of the stars. Recently, however, scientists are finding that artificial light affects the environment and people just as much as it affects plants. Street lights, bright billboards and passing cars, all of these actually manipulate how plants grow, as it turns out. One recent study actually found that heavily lit environments caused plants to release pollen earlier and later in the season than expected; in some unnecessarily bright urban environments, this increase in allergy season can last an additional 130 days!

Plants have evolved over time to rely on their environment in order to accurately gauge the time of year. An increase in nighttime light exposure may lead plants to be confused and think that the days are longer than they actually are. This misinterpretation, as researchers found, led many plants to start producing pollen even earlier in the spring.

Specifically, the research focused on ragweed, a well-known trigger of seasonal allergies, and concluded that ragweed grows larger when subjected to an increase in nighttime light, meaning it can also produce a larger amount of pollen. In addition to this, earthworms which like to feed on ragweed seeds remain buried during periods of artificial light. This leads to more seeds that are available to survive and thrive due to the lack of earthworms to eat them.

While affecting the environment and creating conditions for extended pollen seasons, artificial light affects humans just as much. People are subjected to a continuous ” ambient glow” which negatively impacts our circadian rhythm. This disrupts one’s wake-sleep cycles which can increase allergic symptoms and can lead to exacerbated asthmatic problems. There has even been research showing the correlation between high levels of nighttime light pollution and an increased amount of emergency room visits due to allergic rhinitis and asthma.

It may seem crazy that a streetlight outside your window might be causing you more allergy issues than you realize. Most people still consider factors like the weather to be the true cause of seasonal allergies, but researchers are uncovering more and more about artificial light and its detrimental effects. It is becoming clear that bright cities may be part of the cause of worsening allergies for people like Maya, and dimming those lights might be the first step toward finally breathing easy.