A long, cold winter has allergy doctors and Canadians dreading sneezes and itchy eyes as they prepare for bursts of tree pollen.

Allergist Dr. Mark Greenwald of Toronto is a veteran of nearly 25 years of allergy seasons. Even though trees are still bare, some of his patients are already feeling the effects of a few pollen grains.

"We are already seeing patients presenting with symptoms and they're ramped up because some of the trees are already dispersing," said Greenwald.

In people with indoor allergies, such as to dust mites or cats, the immune system is already primed to react with symptoms to the first release of pollen from trees, Greenwald said.

Greenwald's allergy suggestions include:

  • Don’t brush off allergies because it’s better to address one than having it go on for years when multiple allergies can set in and become harder to treat.
  • Consider committing to years of allergy shots. Studies in Europe suggest that in people with a spring allergy to birch tree pollens, immunotherapy can prevent people from developing allergic asthma compared with those who don’t receive the treatment.
  • Reduce other allergens to which you're exposed. For example, use dust mite encasings on pillows and mattresses to create a barrier so the mites don’t aggravate your eyes, nose and lungs. Use pollen screens on the furnace and windows to prevent pollens from circulating in your home.
  • Use antihistamines, nose sprays and eye drops to control symptoms.
Stanley Park 125th Birthday 20130825

Vancouver is the exception to Canada's slow allergy season this year. (Darryl Dyck/Canadian Press)

"It will be a shorter season, but the load of allergenic material that the person has to deal with will be dumped on them very quickly," Greenwald said.

To do his job, Greenwald said he needs to be part botanist and part meteorologist.

Temperature, humidity, sunlight and cloud conditions, wind, soil nutrients and geographic factors all play a role in trying to predict the severity of an allergy season, he noted.

Microbiologist Frances Coates is an expert in identifying pollen and spores with Aerobiology Research Laboratories in Ottawa. As part of her job, Coates checks a pollen trap daily, one of 30 monitoring stations across the country.

"This year, as everybody can see, the spring has been very slow, very cold and very damp," Coates said. Time is of the essence for trees. "If it stays too cold, too long, trees decide not to release very much pollen."

Pollen season for some trees in Vancouver and Victoria has started, Coates said. Since the field of pollen collection data is so young compared with weather, it’s too soon to identify any trends,she noted.

For areas hit by ice storms, pollen levels could depend on how much of the tree canopy was destroyed. Dead trees won’t produce pollen, but the impact of partial losses of canopy are unclear, Coates and Greenwald said.

"I’m originally from Ottawa so in the Valley there’s always a blast of pollen," said Tamina Eapen at a park in Toronto. "Expect it, deal with it and be ready."

With files from CBC's Kim Brunhuber