Sneezin’ and Wheezin’: Could It Be Global Warming?

Photos by Alex Ramsay/PhotoShelter, Corbis, Tim McGuire/PhotoShelter

There was a time—say, in the last decade—when doctors were quick to point out at least one benefit of getting older: You were likely to outgrow existing allergies or avoid them altogether.

Today, maybe your nose knows otherwise—along with your throat, eyes, skin and lungs.

“Compared to just a few years ago, I’m seeing at least a 50 percent increase in patients in their 60s, 70s and even 80s with allergies or allergic-like symptoms,” says allergist Clifford W. Bassett, M.D., who has a practice in New York and teaches at the New York University School of Medicine and the Long Island College Hospital. “There are many more mature patients with asthma. And in many cases, these are people who never had allergies or asthma before.”

One reason for the increase in sneezing and wheezing: global warming, say some experts.

Growing evidence suggests that increased levels of carbon dioxide in the air—caused chiefly by the burning of fossil fuels and loss of forested lands—are changing the climate, making pollen more abundant and potent.

“The warmer temperatures we’ve been experiencing extend the growing season, which itself increases the growth and potency of tree and grass pollens,” says Lewis Ziska, plant ecologist with the USDA’s Agricultural Research Service. “And carbon dioxide by itself is a source for plant growth. Together, these factors could be the perfect storm for allergy problems, so to speak.”

Ziska is credited as the first researcher to document how global warming could, theoretically, worsen allergies—or even trigger new cases in those previously immune. In 2001 he planted ragweed—the primary cause of autumn hay fever—in urban, suburban and rural sites near Baltimore. Each plot had the same type of seed and soil and the same amount of watering. Yet in the urban plots, where temperatures were higher and the level of carbon dioxide 20 percent higher than in rural plots, the plants shot up in size. They also produced five times more pollen than their rural counterparts, according to a report on Ziska’s study in the Journal of Allergy and Clinical Immunology.

“Carbon dioxide stimulates all plants, but it stimulates weedy plants, such as ragweed, more so,” says Paul R. Epstein, M.D., of the Center for Health and Global Environment at Harvard Medical School. In his study, published in the Annals of Allergy, Asthma and Immunology, ragweed pollen increased by two-thirds when exposed to double the amount of carbon dioxide in the atmosphere now. (Scientists predict the level of carbon dioxide will have doubled by the end of the century.) Meanwhile, other researchers have documented that certain species of trees already produce three times as much pollen as in preindustrial times.

But it’s not just more hay fever that worries scientists. Poison ivy plants are growing larger, sometimes three times the size of those found in 1950, according to a study published last year in the journal Weed Science. “Poison ivy is not only growing larger, but its itch-causing oil is getting stronger because of increased C02,” says Epstein.

Perhaps the biggest concern about rising carbon dioxide levels—and in particular, the burning of fuels such as diesel—is the impact on asthma, which has doubled in prevalence since 1980.

“Airborne pollen binds with diesel particles to go deep into the lungs, where it irritates and can manifest into asthma,” explains Epstein. “And nitrates in diesel also aggravate the same cells that cause allergic reactions. As people get older, their lung function is already compromised for several reasons—smoking, pollution and the natural aging process. So with new assaults, you are more likely to get a reaction.”

In Alaska, long considered anything but a hotbed for seasonal allergies, Anchorage allergist Jeffrey G. Demain, M.D., is also seeing more problems. “Symptoms are stronger and lasting longer,” he notes. In his research, focusing on allergy-causing insects such as yellow jackets, Demain has found rising temperatures in the state are enabling venomous insects to live longer. Compared with the last decade, in some parts of the state there’s been a sixfold increase in cases of stinging allergies that require medical treatment.

“This is especially problematic for older folks who may be allergic and already at risk for anaphylaxis,” he explains. Anaphylaxis, or anaphylactic shock, is a life-threatening reaction to an allergen that causes swelling in the throat and difficulty breathing. It requires emergency medical treatment. “We know that among those with insect venom allergies, there is an increased risk of bad outcome in patients over age 60. That’s because certain medications they take, such as beta-blockers, already increase the risk and severity of anaphylaxis—and the medications we use to control it don’t work as well. Add to that the heart and lung troubles older people have and it doesn’t take much for them to get into trouble.”

Christine Lang, 56, a high school teacher and avid gardener in suburban Philadelphia, says her hay fever has worsened. “When I go outside in the morning and have to literally wipe off a blanket of pollen from my car, I’m very concerned about how much of it I’m breathing,” she says, “and what long-term damage it may be causing.”

Lang adds that she’s increasingly susceptible to poison ivy. “I used to be able to work in my garden, pull out poison ivy and just wash it off with no problem. Now, I scrub my arms immediately afterward and still can’t remove it,” she says. “Whether it’s global warming or just bad luck, there’s no question that I’m suffering more than I used to.”

Sid Kirchheimer, who is based in Philadelphia, writes about health and consumer issues.