Seasonal allergies are getting worse, but newer medications could offer relief

CBC

17-05-2025

Most people with seasonal allergies have likely noticed an uncomfortable trend over the past few years. In parts of Canada, allergy season not only seems to be lasting longer, it seems to be more intense.
Experts like Dr. Anne Ellis, chair of the department of allergy and immunology at Queen's University, say the roughly one in five Canadians who experience respiratory allergies aren't imagining things.
The past few years have brought some seasons with a lot more pollen than Canadians are used to, she told Dr. Brian Goldman, host of The Dose podcast.
"Definitely last year's birch pollen season, and it looks like this year is going to be a doozy as well, has certainly been higher than we've seen in the last 10 years," said Ellis.
Thankfully, newer medications and treatments, including allergy tablets that dissolve under the tongue, are offering seasonal sufferers more relief.
What are seasonal allergies?
Allergic rhinitis, the more technical term for seasonal allergies, is the body's response to stimuli like ragweed, pollen, dust and mould.
Typical allergy symptoms include a runny nose, itchy or watery eyes, as well as coughing and sneezing.
Allergy seasons vary slightly across Canada, says Ellis, adding that allergy seasons in Ontario and Quebec are among the worst in the country.
"We have nice, robust summers with lots of trees and lots of pollen, but importantly also ragweed," she said.
"Come late summer, early fall, we tend to get the biggest hits in terms of seasonal allergies across the country."
Dr. Angeliki Barlas, president of the B.C. Society of Allergy and Immunology, grew up in Saskatchewan and says that she found her seasonal allergies were worse in the prairies than in B.C. But for some of her patients it's the opposite.
"There's different allergens across the country, so it affects everybody differently," she said.
While ragweed is more common in eastern Canada, Ellis said western provinces get a longer tree pollen season instead.
Why are seasonal allergies getting worse?
Experts agree that climate change is the primary driver for worsening conditions across Canada.
"That spring to summer shift has gotten much shorter," said Ellis.
"It just means that it changes how trees pollinate, it changes when the seasons start and stop, and leads to things being different than they were 20 years ago."
In Ontario, Ellis says allergy season used to start around May with pollen, and last into July with a slight reprieve before ragweed season kicked in from around mid-August until the end of autumn.
Now, however, pollen allergies begin when the weather warms up and continue until it starts to snow.
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Warmer temperatures overall mean plants produce more pollen, says Barlas. Plus, it takes smaller amounts of pollen to cause symptoms.
Ellis says there's some evidence that suggests increasing carbon dioxide levels in the atmosphere lead to more allergenic and robust pollen.
Additionally, the long-standing practice of planting male trees in urban areas has exacerbated seasonal allergies, says Ellis.
Female trees bear fruit that creates mess when it drops on sidewalks and in parks, while male trees produce pollen. "So we're getting more allergens in the air because of some of those city planning decisions," Ellis said.
The future of allergy relief?
Over-the-counter antihistamines and nasal sprays can offer temporary relief for seasonal allergies. But allergy shots and sublingual tablets that dissolve under the tongue are longer-lasting immunotherapy solutions, says Barlas.
"You are desensitizing the body to the allergen and you become less allergic — about 30 to 50 per cent less symptoms."
Most people who suffer from seasonal allergies have likely heard about immunotherapy in the form of allergy shots.
Allergy shots can be given year round, and usually consist of six months of weekly injections to help build-up resistance to the problem allergen, followed by monthly maintenance shots for the rest of the year.
Most allergists start their patients on seasonal allergy shots in the fall when pollen counts are typically lower, says Ellis, so that by the time tree pollen season starts in March or April, they only need their monthly maintenance shots.
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In contrast, Ellis says sublingual tablets are taken every day during allergy season, until the first frost, when allergens typically subside, and resume once allergy season starts again.
Ellis acknowledges that allergy shots can be cumbersome for many patients.
"I definitely am prescribing much more immunotherapy in total, but particularly I'd say at least half of my practice has switched to tablets as opposed to injections," said Ellis.
Immunotherapies can only be provided by a certified allergist, and treatment can last anywhere from three to five years, though some patients may need to keep receiving allergy shots to keep their symptoms at bay.
Allergy shots are available for a wide range of allergens, but you can only get sublingual tablets for grass and tree pollen, dust mites and ragweed.
Additionally, a medication used to treat allergic asthma is now receiving attention for its seasonal allergy-fighting potential.
Xolair is the generic name for the omalizumab, a lab-made protein that mimics the body's ability to fight off harmful antigens. It works by targeting IgE, an antibody responsible for allergic reactions, says Ellis.
Xolair isn't currently used to treat allergic rhinitis, but Ellis's patients who take the drug for allergic asthma have noticed improvements in their hay fever symptoms.
In the U.S. it's also used for food allergies, but isn't yet prescribed for that use in Canada, says Ellis.
A 2022 retrospective cohort study looking at Xolair's effects on seasonal allergies found that taking the drug before allergy season "could significantly relieve … related symptoms and reduce medication use." However, that study only looked at the medical records of 64 patients.
Another small study in 2024 that examined its effects on seasonal cedar allergies in Japan, also suggested Xolair can be used to treat allergic rhinitis.
Antihistamines, environmental control are still options too
While more research is conducted on the future of seasonal allergy treatments, Ellis and Barlas say that existing over-the-counter and prescription antihistamines are still relatively effective.
And Barlas says there's no single best treatment option.
"Sometimes you have to do trial and error with different patients in terms of medications," she said.
Nonetheless, experts recommend using some of the newer over-the-counter antihistamines, like cetirizine and loratadine.
"We're trying to move away from first-generation or sedating antihistamines like diphenhydramine, which has a lot of side effects," said Ellis, adding that these medications can cause issues like delirium and other cognitive difficulties.
Stronger prescription antihistamines, like bilastine and rupatadine are also good options.
When it comes to nasal sprays, Ellis recommends inserting the spray into the nasal passages and pointing the nozzle toward the ear, rather than spraying straight up the nose.
"Don't put it into the middle of your nose, because, one, the medication isn't getting where it needs to, and, two, you're more likely to have side effects like nosebleeds, nasal dryness and headaches," said Ellis.
Some research suggests there are "uncommon side effects," including gastrointestinal issues, fatigue, dizziness and confusion.
But Ellis says taking antihistamines every day doesn't usually cause long-term harm, and nor do they really lose their effectiveness if taken every day for many years.
"Sometimes patients have reported to me that they feel like it's not working anymore," she said.
"Chances are good that means you need to move on to something beyond an antihistamine, but certainly it's safe to take an antihistamine on a daily basis all the way through the year if you need to."
Ellis adds that neti pots or other saline sinus rinses are a good non-pharmacological options for patients looking to avoid medication by cleaning the nasal passages of allergens instead.