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, a colleague of Estelle Levetin, a well-known University of Tulsa aerobiologist, detected cedar pollen from Oklahoma in the middle of January 1,050 miles northeast in Ontario, Canada. 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 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.
6. Does wind make seasonal allergy symptoms worse?
Yes, wind matters, which is why your allergist is likely to tell you to stay inside on a blustery day. Trees and plants that depend on the wind to spread their seed churn out light, streamlined pollen granules in the billions, though only a fraction will reach a mate.
The speed and direction of the wind is also emerging as a factor, according to one study from the University of Missouri, and another from the University of Tulsa that used data from New Mexico and Texas. The first found faster winds associated with higher ragweed counts, while the second found winds blowing through heavy juniper regions associated with elevated levels of that pollen.
Similarly, a Turkish study found wind speed was a significant risk factor for high counts of tree pollen. But when it came to grass pollen, this study said average daily temperature and the number of hours of sunshine played the biggest role in pollen counts. For weed pollen, it was mainly the sunshine time. At the University of Melbourne in Australia, an analysis of 16 years of grass seasons in that city found a strong, downward wind associated with the 10 biggest deluges of pollen.
Wind and sun aren’t the only outside instigators. What scientists don’t understand nearly as well, says Levetin, is how factors like humidity affect pollen’s spread. In Tulsa, where she works, the mountain cedar is a major allergy culprit, and its pollen blows into the city from Texas, about 500 miles away. “There are times when I think, it’s not going to be a high pollen day because the humidity’s very high, and the winds aren’t strong. And yet we have terrible pollen,” she says. “We don’t know what’s going on in the upper atmosphere.”
7. How accurate are pollen forecasts?
It’s incredibly difficult to accurately predict pollen levels, and Levetin advises taking pollen forecasts on weather channels and websites with a high dose of skepticism. “Unfortunately, there are a lot of forecasts out there on websites that will give you numbers that I think are pie in the sky,” she says. “I don’t know where they come from.”
Levetin would know. For five years, she’s been involved with an out-of-this-world project that includes NASA as a partner, using satellite imaging to tell when four species of juniper trees, including mountain cedar, are about to release pollen. The satellites have been passing over the Cedars in Texas, Oklahoma and New Mexico twice a day collecting data on colors to pinpoint when immature yellow green cones turn to brown. The scientists are then correlating the measurements from space with ground sampling of pollen levels. Levetin expects to see results from this work soon.
But to improve forecasts, the aerobiologist says North America needs many, many more pollen collection stations and a more efficient, accurate way to identify pollens.The National Allergy Bureau has 84 pollen counting stations across the U.S., Argentina, and one Canadian site, but that pales in comparison to the number of stations in Europe.
It’s labor-intensive work: someone also has to analyze the collected grains, and it can take a couple of hours at a microscope to identify all the types of pollen collected. In the future, a camera connected to a computer could identify what pollens were collected by their shapes, or machines might quickly sequence their genes to pinpoint what they are. Knowing precisely what pollen is present, and how much of it, would help people with allergies take protective measures, Levetin says. “We’re making progress, but it’s expensive.”
8. If there’s more pollen in the air, will more people get oral allergy syndrome?
That is a possibility, says Canadian allergist Ellis. Like other allergists, she has noticed an increase in patients coming to her clinic with the classic symptoms – itching, swelling and throat discomfort – after biting into an apple or munching on raw vegetables.
Oral allergy syndrome (OAS), also called pollen food syndrome, is another medical condition prompted by pollen allergies. Some proteins in fruits, vegetables, and nuts are similar enough to the proteins in tree, grass and weed pollens to prompt the immune system to mount allergic reactions to those foods. This is called a cross-reaction.
Ellis wonders if something is changing in birch or ragweed pollen that makes people more susceptible to cross-reaction. There are no authoritative studies on an increased prevalence of OAS, and Ellis notes that the perceived upswing in cases may simply relate to better awareness among doctors and patients.
OAS reactions involve swelling and itching of the mouth, lips and throat, and often a long grocery list of foods. Fortunately, many with OAS don’t react to cooked fruits and vegetables, as the heat changes the protein’s structure. Anaphylaxis can occur, but only in 1 to 2 percent of cases. In many clinics, new component testing can help an allergist to figure out whether a patient has a true food allergy or OAS.
9. Can scientists genetically modify plants so they don’t make allergy-causing pollens?
Both researchers and inventors are tinkering with the genes of the infamous peanut, in an effort to create a legume that’s safe to eat for those with peanut allergy. Couldn’t they do the same with trees, grass, and weeds?
Theoretically, it’s possible, Levetin says. The challenge would be to modify pollens enough to be unrecognizable to our noses, yet still recognizable to other plants. If you mess too much with pollen, you could disrupt the production of fruit and seeds.
Even if inventors successfully developed hypoallergenic trees and grass, no one can control what their neighbors are planting, or what grows naturally. ‘A lot of what people are allergic to are things that are not produced and sold. Nobody buys ragweed, it’s just there,” Ellis says.
If scientists were successful in creating an allergen-free grass, she notes that there’s nothing to stop it from cross-pollinating with naturally occurring grass. Over time, the hypoallergenic benefits would be lost. Plus, our immune systems do change, so she says there’s also nothing to prevent us from later developing allergies to the supposedly hypoallergenic plants.
10. Could probiotics help prevent seasonal allergies?
Those studying probiotics are seeking to find out whether introducing good bacteria into the gut might help to retrain the allergy-prone immune system to stop reacting to harmless substances, such as pollens. But the jury is certainly out.
One recent study on the usefulness of probiotics to prevent seasonal allergies calls the evidence “promising but conflicting? The small study gave people with grass allergies a daily formula of good bacteria for four weeks, then exposed them to grass pollen. Those who consumed the probiotics were just as congested as those who didn’t, but their noses weren’t as itchy. Another group of people who took probiotics for eight weeks during allergy season had fewer hay fever symptoms, particularly in the second month of taking the probiotics.
The research is in its infancy. Preliminary studies have looked at whether it’s worth the effort to run studies with more patients, and concluded that it is worthwhile. But Ellis says we’ve yet to hear of convincing studies to suggest we should all be chugging back bacteria-containing yogurt drinks daily.
So where do we stand in our approach to seasonal allergic rhinitis? Although the potential for climate change to ramp up pollen allergies is troubling, we do know far more about pollen production than we knew just a decade ago.
Researchers have collected enough years of data to project how the coming temperature fluctuations and carbon emissions are likely to affect plants and us. Doctors are much more aware of oral allergy syndrome, and now have better ways to distinguish it from a true food allergy. Pollen forecasts should improve with time (and money). Even better, new rhinitis treatments are available, with more in development, to help those of us with hay fever to better tolerate the pollen we can’t escape. Pollen may be flourishing in our warmer world, but the prospects for better managing allergies are also bearing fruit.
For tips on managing spring allergies and OAS, check out our outdoor allergy hub: here.