Hay fever: The new wave of effective cures for seasonal allergies

Is it possible to train the body to resist seasonal allergies? That's the hope promised by a new line of immunotherapy that is reviving an old treatment.

Glenis Scadding still remembers one of her first patients for sublingual immunotherapy, forty years later. His hay fever was so debilitating that he couldn't walk to the local train station without wheezing. Scadding's treatment involved desensitising the patient to the culprit of his allergies, birch pollen, with drops under his tongue.

"He turned up at my house with a case of wine, because I had completely altered his life in the spring," says Scadding, vice president of the non-profit Euforea and honorary consultant allergist and rhinologist at University College Hospital London, UK.

"And then I got so much flack, I stopped."

More than 400 million people worldwide experience allergic rhinitis – inflammation of the nasal passages from a reaction to airborne allergens. It happens when your immune system mistakenly identifies something like animal dander or dust mites as harmful, triggering symptoms that can include a runny nose, itchy eyes, sneezing and – at its worst – breathing difficulties. When it's seasonal, such as in response to pollen, allergic rhinitis is called hay fever.

As well as affecting quality of life, hay fever can have severe long-term consequences, including the risk of developing both respiratory infections and asthma.

Plus, it affects a lot of people. In the UK, around one in four adults and one in eight children have allergic rhinitis, leading to at least 16 million doctor's office visits per year, with similarly high figures in Australia and the US. And that number may be growing: studies find an increase in prevalence over time in regions including Europe, the US and Australia. There is also growing evidence that hay fever symptoms are becoming more severe with climate change.

Yet there is good news, say allergists: high-quality, effective, and safe therapies are now available for hay fever. Most treat symptoms. But one, allergen immunotherapy (AIT), is more of a cure, "teaching" the body to react less to certain allergens, and it may re-route the common hay fever-to-asthma pathway.

Far more people could benefit from these treatments than are receiving them. "Very few people get to see the right person to treat their disease – and they don't get to see them at the stage when the disease is early, uncomplicated and easy to treat," says Scadding.

A serious health concern

Part of the problem is that even health professionals don't always take allergic rhinitis seriously, says clinical allergist Stephen Durham, emeritus professor of allergy and respiratory medicine at Imperial College London and Royal Brompton Hospital. General practitioners often tell patients just to go to the pharmacy for an antihistamine, for example, rather than referring them to an allergist or considering something preventative and long-term, like allergen immunotherapy, he says.

"Hay fever is a major problem, and it's often trivialised by those who don't have it," Durham says. "If you think about what we do in life, we work, we sleep, and we have fun. And all of those things are seriously impacted by hay fever."

Hay fever sufferers are more likely to have difficulty falling and staying asleep, to feel fatigued and to wake frequently at night, for example. Seasonal allergies have even been found to impact children's academic performance.

There can be other health consequences, too. Because their mucous membranes are chronically inflamed, people who have an allergy experience more respiratory infections – up to twice as many, according to one study. When it isn't adequately treated, hay fever can cause severe, chronic upper airway disease and ear infections.

Hay fever, particularly in children, can also lead to the development of asthma, and asthma itself tends to be more severe among people who also have hay fever. "There's a concept of 'one airway, one disease'," says Barrie Cohen, a paediatric allergist in New Jersey, US and author of a 2023 American Academy of Pediatrics review on allergic rhinitis. Inflammation in the upper airways can influence the lower airways through shared immune pathways, she says. And that can lead to asthma.

A century-old problem – and solution?

While hay fever is on the rise, its existence is not new. Based on his own experiences and those of 28 other patients, the London physician John Bostock detailed seasonal symptoms as far back as 1828. His descriptions included "fulness of the head, stoppage of the nose, sneezing, watering of the eyes, and discharge from the nostrils".

Immunotherapy for allergens like pollen isn't new either. In 1911, another doctor had found that injecting hay fever patients with grass pollen extract could lessen their symptoms the following spring. The first double-blind, placebo-controlled trial for grass pollen immunotherapy was held in the 1950s.

By the 1980s, this became a recognised treatment. These "allergy shots" proved highly effective, easing the sneezing and suffering of thousands of patients. But there was a problem. "Injection immunotherapy has occasionally killed people," says Scadding, due to anaphylaxis – an allergic reaction to the shot itself.

These events are extremely rare, occurring in about one per 2-2.5 million injections, and today, thanks to a better understanding of risk factors and of proper administration, they are rarer still.

But when about 26 anaphylaxis-related deaths from subcutaneous immunotherapy were recorded in the UK from 1957 to 1986, the UK passed new regulations – including, at the time, that anyone who received an injection had to wait at the doctor's office for observation for two hours. (Now, it’s 30 minutes). Since injections have to be given regularly, often weekly, this requirement made subcutaneous immunotherapy onerous.

Interest increased in the oral alternative that Scadding had been pioneering in the 1980s. Sublingual therapy, as it is known, involves placing droplets of the allergen under the tongue, rather than being injected into the arm. There was initially some scepticism that it could work as well as the shots.

"Sublingual was regarded as a real 'fringe' thing which wasn't going to work," Scadding says. "So I stopped doing it for a while." But the trials suggested that it provided much lower risk of anaphylaxis than its subcutaneous counterpart, while still being highly effective. "There have been no fatalities. Serious adverse events are very rare," Scadding says. She notes local reactions, like temporary itching or swelling of the tongue, are more common.

By 1998, the World Health Organization published a consensus statement on allergen immunotherapy that included under-the-tongue administration as a promising alternative to the shot – legitimising the therapy on a global scale.

As with allergy shots, the main challenge is sticking with it. A tablet should be taken under the tongue every day for between eight and 16 weeks before the pollen season begins, Durham says. Starting 16 weeks in advance controls symptoms through the summer in some 85% of patients.

The recommendation is to keep taking it, year-round, for three years. "If you treat people for three years, you can induce long-term disease remission," Durham says. In one clinical trial he ran, participants with a grass pollen allergy who were given a placebo reported having severe hay fever symptoms on 16% of days during the allergy season; those who received sublingual droplets reported it at 6%.

Long-term relief

Even more excitingly, he says, there is evidence that the changes are long-lasting. Several trials, including one of more than 1,000 participants in Japan, found that sublingual immunotherapy improved symptoms as long as two years after stopping.

The main problem with the sublingual therapy, experts say, is that the types of allergy it can treat are still limited. The only sublingual immunotherapies approved by the US Food and Drugs Administration are for dust mites, ragweed pollen and grass pollen. "A lot of my patients have tree pollen allergy – I can't really help them if I want to use an on-label, FDA-approved product," says Cohen. As a result, she frequently recommends an allergy immunotherapy shot instead.

Whether through oral droplets or injection, allergen immunotherapy has proven effective for thousands of patients. One study comparing the medical records of more than 45,000 allergen immunotherapy patients from 2007 to 2017 with those of people who had been diagnosed with allergic rhinitis but did not receive any type of immunotherapy, found that immunotherapy patients had greater reductions in both hay fever and asthma-related prescriptions than the control group. They were also less likely to be diagnosed with pneumonia.

Allergen immunotherapy may even prevent the onset of asthma. One randomised, double-blind trial of more than 800 children with grass pollen allergy, aged five to 12, compared those who received sublingual immunotherapy to those who received a placebo. At a two-year follow-up, children who received the allergen drops were about 29% less likely to have developed asthma symptoms or used asthma medication than the placebo group.

Already having asthma, however, can be a contraindication for undergoing allergen immunotherapy in the first place, particularly if the asthma is severe or uncontrolled. This is because, while anaphylactic shock remains extremely unlikely, the risk is greater when airway inflammation is already present. For those patients, or those for whom allergen immunotherapy alone doesn't work, there's another option: biologics, a class of medications that target key immune pathways involved in allergic reactions, halting the body's inflammatory response.

In some cases, biologics might be given alongside allergen immunotherapy, a combination that has been found to decrease the odds of severe nasal symptoms by about 59% compared with immunotherapy alone. "But they don't induce long-term disease remission like immunotherapy," Durham says. "And they cost between £12-20,000 a year while, for example, the immunotherapy that we've been talking about – those tablets cost less than £1,000 ($1,300) a year."

How to pick medications and reduce triggers

Such prices and the duration of these treatments can be a major barrier for many patients. So what are the other options?

"The single most effective treatment that we have that patients can easily access is a spray which has antihistamine as well as corticosteroid in it," Scadding says. They outperform either medication on its own, she adds.

Durham agrees. What is especially important, he says, is to start the treatment before the season begins, and take it regularly – even on days you don't have symptoms. "If one does that, then it's highly effective not only at treating symptoms, but also preventing attacks," he says.

More like this:

• The habits that prevent allergies

• How your pets alter your immune system

• Six myths (and truths) about hay fever

It is also crucial to administer the spray properly, allergists say. (See how to apply your nasal spray, above).

Oral antihistamines aren't usually as effective, says Scadding. They aren't applied directly to the nasal tissues – where allergic reactions occur – so tend to be weaker and take longer to work. But if you do take one, ensure it is one of the newer ("second-generation") medications, like cetirizine or loratadine. As well as being more effective, they are less sedative: first-generation medications can induce tiredness to the point that they have been found to raise the risk of a car crash.

Reducing triggers is also important. Allergists recommend keeping windows closed, using an air purifier, and wearing sunglasses or a mask when you go outside. Washing your hands, face and eye area – and, ideally, showering, including hair – when you come in, especially before going to sleep at night, can also help, says Cohen: "If you're sleeping in that pollen on the pillowcase, you can imagine it's not good to breathe in."

Still, particularly if you suffer from severe symptoms, there's only so much reduction that can be done. And given that walks, cycling to work or throwing around a ball outside can be everyday pleasures that enhance our quality of life – especially as the weather warms – it's not always optimal, either.

"We've got very effective treatments for the majority of patients," Durham says. "The message is that it's trivialised, and people don't understand how to treat it properly."

* Amanda Ruggeri is a journalist who explores the science, psychology and history of the ideas we take for granted. Her upcoming book on sleep will be published by BenBella in summer 2027. She is @mandyruggeri on Instagram, Threads and TikTok.

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