For the millions of sufferers who can't keep their eyes from watering or their throat from itching, this spring feels like the worst allergy season ever – and, according to allergists in Canada and the United States, that's not far from the truth.

Through a combination of circumstances – a snowy winter, a delayed spring – North Americans are being deluged with pollen.

Normally, allergens are released at different times. Oak, birch and other tree types are the first to release their pollen. They're followed by seasonal trees such as ash and poplar, before grass releases its pollen in June to early August.

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This spring, the timing is off by two to three weeks due to a lingering winter which, in turn, has led to an amalgamation of pollens. Clifford Bassett, the medical director of Allergy & Asthma Care of New York, described how the pollen from early and mid-spring trees mixed with the grass pollen in "a triple whammy … to create misery and suffering."

Surveys, including one conducted in 2010 for the pharmaceutical company Johnson & Johnson, have shown that more than eight million Canadians have an allergy with symptoms of one kind or another – coughing, constant sneezing, a runny or stuffy nose. These are caused by the body's immune system, which releases the chemical histamine to respond to incoming particles of dust and pollen. Research says we inhale several hundred grains of pollen with each breath.

"Whenever you have a fall and winter with a lot of precipitation, the soil is moist," said Dr. Bassett, noting how that moisture makes for ideal growing conditions for plants to produce more pollen. "That's how you will get to experience the wonderful effects of allergies."

Given the abundance of snow that fell in parts of Canada this winter, much of it in Ontario and the Maritimes, people with allergies in those areas are likely to suffer to a greater degree and, in some cases, for a longer period of time.

"I hear this almost every year or two, 'This is the worst it has ever been,'" said Susan Waserman, a professor in the division of clinical immunology in McMaster University's department of medicine. She added the problem this spring has been the overlapping of trees and grass, making matters more intense. "It is about getting all the pollen at the same time," she said.

While it didn't snow as much in Alberta, allergies were still afforded an ideal place to grow and spread.

"Every year the media does a story about allergies," said Joel Doctor, a clinical immunology and allergy specialist in Calgary. "That said, this year may turn out to be the most severe pollen season we've had. The conditions [that work best for pollination] are dry, warm and windy. That's been Calgary over the past few months."

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Allergy sufferers deploy an array of remedies, from antihistamines to immunotherapy – allergy shots containing a tiny amount of the substance that triggers the allergic reactions. Michele Swanky's allergies are at their worst in the spring and fall. The Calgary mother takes an emergency inhaler with her at all times since her allergies can trigger an asthma attack. Her two adult sons also suffer from allergies and have since they were kids.

"One of my sons has it really bad right now. His eyes are red and swollen," Ms. Swanky said. "When the boys were younger we did everything we could at home. We ripped up the carpets, got rid of old furniture. We kept the windows closed. We were pro-active."

With springtime finally reaching the Maritimes, people there are only now beginning to experience allergic reactions. It's an upsurge in pollen levels that has increased traffic to Halifax Allergy and Asthma Associates, according to Sandy Kapur, whose specialty is treating children with allergies.

Allergists have seen an increasing number of kids over the past generation, which in turn has led to a better understanding of allergens and how to treat them. There are also more items being added to the allergy list – newcomers such as flax, kiwi, sesame and mustard seed. Dr. Kapur says parents need to prepare for allergy season and have the proper medications ready.

"Look at the Canadian population: 20 per cent have some form of allergic disease. That's one in five people," Dr. Kapur said. "We have better ways to [now manage the disease] with appropriate planning and starting treatment early."