How Climate Change Is Making Allergies Worse

As global temperatures continue to rise, allergy seasons are growing longer and more intense. But for millions of people worldwide, seasonal allergies are no longer just a minor inconvenience—they’re becoming a serious public health concern, driven in part by extreme weather events like “thunderstorm asthma”.

One of the most alarming examples occurred in Melbourne, Australia, in November 2016. A sudden thunderstorm lifted enormous amounts of pollen into the air, where moisture and lightning shattered the grains into microscopic particles. These particles were then swept back to ground level, where they were easily inhaled. Emergency services were overwhelmed. Thousands struggled to breathe. Ten people lost their lives.

This phenomenon, known as thunderstorm asthma, is rare but deadly and experts fear it may become more common as climate change accelerates. Rising global temperatures are increasing both pollen levels and the frequency of extreme weather events, creating a dangerous combination for people with respiratory conditions.

Pollen, though vital for plant reproduction, is also a major allergen. Some plants, like ragweed, grasses, and certain trees, release pollen into the air, where it can easily be inhaled. In people with allergies, the immune system misidentifies this pollen as a threat, triggering symptoms such as sneezing, itchy eyes, or even asthma attacks.

And the problem is only getting worse. Research shows that as carbon dioxide (CO₂) concentrations rise, many plants produce significantly more pollen. In fact, experiments reveal that ragweed exposed to elevated CO₂ levels not only grows faster and produces more pollen, but also emits a more allergenic form of it—one that provokes stronger immune responses.

Across North America and Europe, studies have found that pollen seasons now start earlier, last longer, and produce more pollen than they did just a few decades ago. In the U.S., for instance, the average pollen season in the 2000s began three days earlier than in the 1990s—and pollen counts were 46% higher.

By 2050, scientists estimate that ragweed pollen concentrations in some areas could be up to four times what they are today, particularly in regions where the plant has spread aggressively. Even areas that haven’t yet experienced significant ragweed exposure—like parts of the UK and Germany—are expected to see a dramatic increase in pollen loads due to warming climates and shifting plant habitats.

Urban environments can make the situation worse. Some cities have historically favored planting male trees, which don’t bear fruit but release large amounts of pollen—a practice dubbed “botanical sexism” Combined with poorly managed green spaces and limited allergen monitoring, this creates a high-risk environment for allergy sufferers.

There are actions we can take. Controlling the spread of allergenic plants, choosing low-pollen tree species for city planting, and improving pollen and allergen forecasting systems can help mitigate the effects. Historical efforts like New York City’s “Operation Ragweed” in the 1950s managed to reduce pollen levels significantly through targeted removal.

However, experts agree that without urgent efforts to reduce greenhouse gas emissions, the impact of allergies will only grow more severe. People around the world may face longer periods of discomfort, higher risks of asthma, and potentially life-threatening events linked to extreme weather.

“The science is clear” says Paul Beggs, an environmental health researcher in Australia. “Climate change is already affecting our health—and if we don’t act, it’s going to get much worse”.