Almost half of the UK population struggle with hay fever symptoms, according to a survey by Allergy UK – nearly double the number previously thought.

The issue, also known as seasonal allergic rhinitis, occurs when your body has an allergic reaction to pollen – typically when it comes into contact with your mouth, nose, eyes and throat.

It was previously estimated to affect somewhere between 10 and 13 million people in the UK, or 20-30% of the population. But a survey of 7,000 people by Allergy UK and Kleenex reveals that far more people may be struggling.

There’s also been a “significant increase” in the number of those with the allergy – more than a third (37%) said they had developed symptoms for the first time in the last five years. 

So, what’s behind the rise?

There are a few working theories. Allergy UK suggests the increase may be closely linked to rising temperatures in the UK. Amena Warner, head of clinical services, says evidence suggests climate change and increasing temperatures may contribute to extending the grass pollen season in the UK – and grass pollen is the cause of the majority of pollen-driven hay fever symptoms.

“Human activities have increased atmospheric concentrations of carbon dioxide (CO2) and other greenhouse gases,” explains Warner. “Studies show plants produce more pollen as a response to high atmospheric levels of CO2, so people may find their hay fever is worse when pollution levels are high, especially in warm weather.

“These are the factors that lead us to expect rising pollen levels in the UK in the coming years, triggering the unpleasant symptoms of hay fever over longer periods.”

The London Allergy & Immunology Centre also suggests this may be the case –noting that warmer temperatures caused by global warming are extending our summers, meaning the periods in which pollen is released are longer than usual – and so symptoms are prolonged.

This is bad news for those with allergies – and for those without. Professor Leonard Bielroy, an allergy specialist at Rutgers University Centre of Environmental Prediction, believes the more exposure you have to an allergen, the more likely you’ll become sensitised to it. This could help explain why more people are becoming susceptible to pollen allergies in the past five years. 

Immunologist Professor Daniel Altmann, from Imperial College London, shares another hypothesis for the rise, suggesting it’s not limited to hay fever.

“The working hypothesis for the ongoing creep of allergic disease over the past several years has been the ‘hygiene hypothesis’ – the idea that our immune systems were programmed during millennia of evolution to deal with quite a dirty planet, including bacterial infection and common parasitic infestations,” he tells HuffPost UK. 

With all of the washing, scrubbing and disinfecting as we’ve become cleaner, we may be left with an “inappropriately programmed” immune system, making us susceptible to allergy and asthma, he suggests. “During this past year in lockdown, we’ve all lived in our homes in an even cleaner microbiological environment. It could be that we’ll see yet more allergy in the future.”

The Allergy UK study revealed the negative impact of hay fever on people’s quality of life. Nearly two thirds (64%) reported tiredness due to poor sleep quality, while a third (34%) have skipped social engagements due to symptoms.

Workers said hay fever affects their concentration (46%) and lowers their productivity (35%), while a third of sufferers reported experiencing embarrassment and anxiety due to their symptoms. Despite this, 44% have never discussed their hay fever with a healthcare professional.

Amena Warner from Allergy UK said hay fever can sometimes be trivialised, but the latest research illustrates its real impact on the millions of people across the UK who experience it each year.

“We know anxiety about the condition has become worse during the pandemic and we urge anyone who is suffering in silence to speak to a pharmacist or healthcare professional to help find treatments that work for them,” she said.