We narrow down readers’ frequently asked questions, while our expert sources turn to lab experiments, studies, and even satellites orbiting the planet to offer up answers.
1. Can I outgrow a pollen allergy?
“We used to think so,” says allergist Dr. Richard Weber, which is not what many of us want to hear. Conventional understanding from earlier in the 20th century was that seasonal allergies peaked in a person’s 20s, 30s and 40s, then often faded in middle and old age. Weber, a professor of medicine at National Jewish Health in Denver, says something is changing, and that no longer appears to be the case.
Today, tests show allergic antibodies are sticking around in the bloodstream later in life, and some patients in their 50s and 60s are reporting new hay fever symptoms that they had never before experienced.
Allergies, asthma, and the itch and dryness of eczema have all become more prevalent in Western countries in the past 50 years. Weber says it may be that we’re exposed to different pollens, or more of it, or that pollen seasons are longer, thanks to climate change.
At her clinic, Dr. Anne Ellis, an allergist and associate professor of medicine at Queen’s University in Canada, also has some adult patients turning up who’ve never had seasonal allergies before. There’s no clear answer why these new sensitivities seem to occur out of the blue. “It can be really dramatic when somebody moves from one location to another, even within the country, or moves to the U.S. Northeast or Canada from a place where an allergen like ragweed isn’t so prevalent,” she says.
Pollen grains themselves are too large to get into the lungs, says Weber, if who has been studying pollen and how it triggers allergies for 35 years. However, within the cocktail that pollen grains release when they land in the nose are smaller particles coated with allergy-stimulating proteins.
These coated particles are small enough to inhale deeply into the lungs.
They travel down your airways, meet up with IgE antibodies that your allergy-prone immune system produces to protect against them, and this sets off irritation and swelling in lung tissue.
Unlike your nose, Weber says, the airways have smooth muscle lining the bronchial tubes. Some of the chemicals released in response to pollen proteins cause the smooth muscle cells to contract, leading those with asthma to wheeze as the air whistles through the constricted pipes.
3. Are some pollens more aggravating than others?
Some pollens, like that of the birch tree, are considered more allergenic. Pine, on the other hand, gives off a lot of pollen, but tends to cause less hay fever grief.
The experts say, however, that it’s really not so much one pollen versus another, but what you’re specifically allergic to, what’s growing in abundance in your community, and how much of the allergen you will be exposed to.
Weber points to a study showing that in a single year, an alder tree can produce 7.2 billion pollen grains, while a birch can disperse more than 5.5 billion grains. You can certainly be allergic to an oak tree’s allergen, but an alder will be producing seven times the pollen.
In California, it might be eucalyptus and camphor that are your undoing. In the southwestern U.S., juniper and olive trees are some of spring’s biggest irritants, and if you live in Texas, “cedar fever is a real thing,” Weber says. Junipers and elms are troublemakers from the Midwest down to Florida, and New Englanders best steer clear of pine, oak, and mulberry trees.
In Canada, those on the west coast will find red alder and Garry oak their nemeses, while those farther east have birch, elm, maple, oak and poplar to blame for their pollen symptoms.
4. How far can pollen travel?
The answer will surprise you. In 1998, one of Levetin’s colleagues 1,050 miles northeast in Ontario, Canada detected cedar pollen from Oklahoma in the middle of January. It took about a day and a half to get there.
Weber points to a case where researchers found pollen on the remote south Atlantic island of Tristan da Cunha – at least 2,800 miles from where it naturally grows in South America.
More commonly, you should expect to be exposed to pollen from several blocks away, from trees lining civic boulevards to your local schoolyard.
5. Is climate change affecting people’s pollen allergies?
Yes, climate change is implicated in aggravating pollen allergies in three ways. First, by either lengthening the pollen season or moving it earlier or later, so there’s less; overlap between grass and tree pollination time. The second way is by expanding the area where a plant can grow, exposing people to new pollens. The third means is by stimulating plants to churn out more pollen than they ever did before.
A seminal study found that, thanks to climate change, the autumn ragweed pollen season is getting longer, particularly in the Midwest and the Canadian prairies. The study took 15 years of pollen counts and weather data from a band of cities stretching from Texas to Saskatchewan, and compared the annual length of ragweed’s pollen season.
The result? Since 1995, ragweed season north of the 44th parallel is from anywhere from 13 to 27 days longer. “This does mean suffering in the north,” says well-known University of Tulsa aerobiologist Estelle Levetin.
At the same time, plants are slowly migrating north, bringing their allergenic pollens with them. For instance, several spruce species are expanding north in Alaska, Canada and Sweden. Levetin says aerial photography also shows shrubs in parts of Alaska where they weren’t seen 50 years ago.
Then there are the chemical changes of climate change: the growing concentrations of carbon dioxide, ozone and nitrogen dioxide. A USDA review concludes that plants thrive in higher carbon dioxide environments, sprouting more flowers and producing more pollen. Plants exposed to carbon dioxide and ozone may also produce pollen with more allergenic proteins – a double whammy for those with hay fever.
Next: Can you really trust pollen forecasts?