Seasonal allergy sufferers are facing more pollen for longer periods as temperatures rise, while experts say global warming is also setting off increasingly alarming extreme allergy events.

According to a report by the BBC on Saturday, emergency rooms in Australia saw eight times the usual number of people arriving with breathing issues and nearly 10 times the typical number of asthma-related hospital admissions.

A total of 10 people lost their lives including a 20-year-old law student who collapsed on her lawn while waiting for an ambulance as her family attempted to resuscitate her, and one survivor recalling how he had been breathing normally before finding himself gasping for air within just 30 minutes, describing the experience from his hospital bed as "insane".

World grapples with thunderstorm asthma

"It was an absolutely massive event. Unprecedented. Catastrophic," Paul Beggs, an environmental health scientist and professor at Macquarie University in Sydney, Australia, described the incident, adding that "The people in Melbourne, the doctors and the nurses and the people in pharmacies – they all didn't know what was happening."

It soon became evident that this was a large-scale case of "thunderstorm asthma", a phenomenon that happens when specific types of storms break pollen particles into smaller fragments, releasing proteins that rain down on unsuspecting individuals and potentially triggering allergic reactions even in those who have never previously had asthma.

According to the report, thunderstorm asthma events like the one in Melbourne are a striking example of how climate change is intensifying pollen-related allergies, with rising temperatures causing longer allergy seasons, more severe symptoms, and increasing numbers of people affected in regions like the US, Europe, and Australia, according to scientists.

This year in the US, pollen levels are expected to surpass historical averages across 39 states, with experts warning that this trend is only likely to intensify in the coming years.

While Melbourne has been the unfortunate epicentre of thunderstorm asthma, with seven major events since 1984, similar incidents have occurred in places like Birmingham and Atlanta, and although still rare, climate change may be making them more likely by extending pollen seasons and increasing extreme weather like storms.

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"We know that climate change is leading to greater amounts of pollen in the atmosphere," Beggs told the BBC, adding that "It's changing the seasonality of the pollen. It's changing the types of pollen that we're exposed to."

Allergy seasons begin earlier, last longer

One factor is the rise in temperatures, which is causing pollen seasons – the periods when plants release pollen, usually in spring and summer – to begin earlier and extend for longer durations, according to Elaine Fuertes, a public health scientist specializing in the environment and allergic diseases at the National Heart and Lung Institute, Imperial College London.

Fuertes explained to the BBC that this shift means more people are likely to start experiencing symptoms earlier in the year and continue dealing with them for an extended time.

In regions like the US and Europe, one major contributor is ragweed – a common group of flowering plants often seen as weeds – with various species worldwide known to release massive amounts of pollen, as just one plant can emit up to a billion grains, growing not only in gardens and farmland but also in hidden corners of urban spaces.

Ragweed pollen allergies already impact around 50 million people in the US alone, and a study that examined data from 11 locations across North America between 1995 and 2015 found that 10 of those locations saw their ragweed pollen seasons grow longer – in some cases significantly – with the season extending by 25 days in Winnipeg, Manitoba, 21 days in Fargo, North Dakota, and 18 days in Minneapolis, Minnesota over that 20-year span.

According to the report, without rapid reductions in greenhouse gas emissions, the situation is expected to worsen, with a 2022 study projecting that pollen seasons could start 40 days earlier and end 15 days later by the century's end, potentially extending hay fever symptoms by two months annually.

Concentration of allergens on the rise

Not only are people facing longer exposure to allergens, but the concentration of allergens in the air is also rising in many regions, with the US pollen season in the 2000s starting three days earlier than in the 1990s while pollen levels surged by 46%.

The increase in airborne allergens is partly driven by rising atmospheric CO2 levels from human emissions, which benefit many plants that trigger hay fever, as studies show that grass grown under 800 ppm CO2—a projected future level—produces 50% more pollen than when grown under current 400 ppm conditions.

Research on oak trees—a major hay fever trigger in countries like South Korea—reveals that under elevated CO2 levels of 720 ppm, pollen production skyrocketed to 13 times the amount seen at current 400 ppm conditions, while even at 560 ppm, pollen counts were 3.5 times higher than today's levels.

What can be done?

It might be possible to make some drastic but direct interventions, for example. A century ago, some US cities even set up commissions to tackle ragweed. "Chicago employs 1,350 in hay fever fight," blares one headline from 1932. The news story explains that men – otherwise unemployed during the Great Depression – were paid the equivalent of one week's food and lodging (and "25 cents in cash") for each day they spent cutting down the plant.

Such efforts proved effective, with a 1956 study showing New York City's "Operation Ragweed" reduced pollen production by roughly 50% through mass plant removal, while current European initiatives demonstrate ongoing coordinated action—Berlin deploying teams to eradicate ragweed and Switzerland implementing a 2024 import ban while organizing volunteer patrols to remove the plants from public parks.

Scientists emphasize the critical need for pollen monitoring and forecasting, with Beggs stating, "We need to know what we're breathing in. That's a pretty fundamental thing in terms of our health," and noting that while real-time weather data is widely available, reliable allergen tracking remains scarce despite its health implications.