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Allergy season in Canada starts in April and lasts for some into the fall.Aleksei Morozov/iStockPhoto / Getty Images

Canada’s springtime allergy season is getting under way, but if you suffer from pollen allergies, you likely already know this. Here’s everything you need to know about allergies and how to cope.

When is allergy season at its peak?

The beginning of allergy season varies year to year, depending on weather patterns and warming in different areas of the country.

Tree pollen is the most common cause of springtime allergies, and their counts peak from late April to May.

Grass and weed pollen are highest in the summer months, from May to mid-July and again in fall, around mid-August to October.

The Weather Network provides local pollen counts for many locations across Canada via Aerobiology Research Laboratories, a company that specializes in allergen forecasting.

What causes seasonal allergies?

Seasonal allergies are caused by pollen from plants, usually those from trees, grasses or weeds. These are small, light and dry, and easily picked up by the wind to travel long distances. Flowers also make pollen, which can be spread by insects, but this kind is less likely to cause symptoms as there is much less of it.

Symptoms develop because your immune system is responding to the pollen molecules as if they’re intruders. In response, it releases chemicals, such as histamines, leukotrienes and prostaglandins, which trigger the symptoms you experience.

What are the symptoms of seasonal allergies?

Symptoms vary from person to person. The main ones are:

  • Itchy, watery eyes
  • Sneezing
  • Runny, stuffy, or itchy nose
  • Temporary loss of smell
  • Headache and fatigue
  • Dark circles under the eyes
  • Drainage from the nose down the back of the throat, known as post-nasal drip
  • Sore throat or coughing
  • Snoring

Are seasonal allergies getting worse?

A decade ago, The Globe reported on rising asthma and allergy rates and the mounting evidence that hay-fever season was lasting up to a month longer than in the past, and parts of Canada that were once too cold for ragweed and other allergy-inducing plants were seeing activity for the first time.

Dr. Anne Ellis, a professor and division chair in the department of medicine at Queen’s University, told The Globe’s Decibel podcast host last year that they’ve seen record pollen counts. They say seasons that used to be separate – tree pollen season and grass pollen season – are overlapping, making allergy season much worse for people who are allergic to both.

Dr. Ellis says that changes in weather patterns are “almost certainly driving some of the changes we’re seeing to pollen seasons.”

Urban planning is also partly to blame. Cities often opt for male plants, as the female plants bear potentially messy fruit. Male plants, however, are the ones that release pollen.

How to treat allergy symptoms

To treat seasonal allergies, HealthLink B.C., the province’s telehealth service, recommends some home remedies, such as cleaning the inside of your nose with salt water, using a humidifier in your bedroom and taking hot showers.

Over-the-counter allergy medicine can also help with symptoms and steroid nasal sprays can clear a stuffy nose.

To help with itchy, watery eyes, they recommend trying a non-sedating antihistamine, such as fexofenadine or loratadine, which can be bought over the counter.

How to prevent and minimize allergy symptoms

There are a few ways to prevent or minimize seasonal allergies, by doing things like reducing exposure to pollen by keeping your house and car windows closed, limiting time you spend outside during midday and afternoon when counts are higher, or wearing a pollen or dust mask and pollen-blocking cream for your nostrils when you can’t (or don’t want to) avoid being outside, according to Thomas Leo Ogren, author of The Allergy-Fighting Garden.

The California-based horticulturalist has studied allergens for decades, and says gardening on calm days after heavy rains can also minimize allergen exposure, as can choosing plants with allergies in mind, using gravel or oyster shells instead of wood-based mulch, which retains moisture, and attracting birds to the garden to eat insects that trigger allergies.

After spending time outside, you can also shower, change clothing and rinse your eyes with cool water or saline when you return indoors to remove any pollen that’s come inside with you.

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