Hay fever strikes people of all ages, with different allergens active different times of the year.

In some parts of the world, up to 30% of people have allergic rhinitis. This type of allergy is caused by sensitization to foreign proteins present in pollens and spores, and this type of sensitization is present in up to 40% of the population, though the severity of the reaction can sometimes be very mild.

Allergic rhinitis causes tens of millions of physician office visits every year, and plenty of suffering by people who cope using over-the-counter remedies. Symptoms include itchy, watery eyes, runny nose, sneezing, and post-nasal drip, which can result in an annoying, chronic cough. Scientists who study common allergens like pollen and mold spores have performed research indicating that as carbon dioxide levels in the atmosphere climb, pollen counts go up, and this could spell more misery for allergy sufferers.

Grass Pollen and Elevated Carbon Dioxide Levels

In November, researchers from the University of Massachusetts Amherst published results from a study showing that increasing levels of carbon dioxide in the atmosphere elevate levels of grass pollen significantly – up to 200%. To determine how plants release pollen in a climate changed by elevated levels of carbon dioxide, the scientists grew grass plants in pots that were placed in chambers called continuously-stirred tank reactors, which allow the plants to be grown under different gas concentrations. Ozone and carbon dioxide levels were increased to correspond to climate change conditions.

When the grass plants flowered, the researchers counted pollen production and levels of a protein called PhI p5, which is what causes the allergic reaction suffered by so many hay fever sufferers. Typically, higher ozone levels repress pollen and allergen production in some types of grass, but the elevated ozone levels in the experiment could not cancel out the profound effects of elevated carbon dioxide, which caused pollen levels to soar regardless of ozone levels. The researchers chose grass to study because people worldwide are exposed to grasses, so pollen production from them would affect large portions of the world’s population.

Mold Spores and Climate Change 

At last year’s annual meeting of the American Geophysical Union, a scientist from the Weizmann Institute of Science in Israel presented research showing that a common fungus (Aspergillus fumigatus) is more allergenic in the presence of higher carbon dioxide levels. The fungus is found in decomposed biomass and soils, plus manmade locations like the insides of walls and air conditioning filters.

Spores coated with tiny proteins are responsible for producing allergic reactions, which can be as mild as sneezing or as serious as anaphylaxis and lung infections. The research team grew mold spores in the presence of different levels of carbon dioxide and then measured the presence of allergenic proteins produced by the spores. Mold grown at current atmospheric carbon dioxide levels produced 8.5 times as much of the protein as mold grown at carbon dioxide levels representative of the pre-industrial world, and this could cause those with mold allergies to have greater problems.

Ragweed Pollen and Higher Levels of Carbon Dioxide

Ragweed pollen is a major cause of allergy symptoms in North America, and a Pittsburgh immunologist has studied ragweed pollen levels using an artificial “nose†that traps spores. Daily pollen counts are collected for allergists, weather reporters, and allergy patients. This and other data collected on ragweed pollen has shown that the volume of ragweed pollen appears to be increasing in many areas, and that in Canada, the ragweed season is almost a month longer now than it was 20 years ago. Extended ragweed seasons have been identified in many areas, but the effect is less pronounced the farther south the data is collected.

Extended ragweed seasons could prolong the misery of allergy sufferers who love the outdoors.

What Doctors Are Reporting

But what are doctors seeing in their practices? Many of them are seeing more allergy patients. Dr. Leonard Bielory of Rutgers University told Michigan Radio, “I saw a hidden signal in the pollen count changing over time. And I started correlating that we’re seeing patients earlier and more patients — the volume seems to be increasing. And some who were moderate or mild in years past are now more severe.”

Dr. Cliff Bassett, fellow for the Asthma and Allergy Foundation of America says he’s seen pollen season start two to four weeks earlier in the spring due to earlier thaws. Furthermore, ragweed season is lasting longer in the fall. He told Weather.com, “In the fall, ragweed season is three to four weeks longer.†This is corroborated by Agriculture Department studies showing that ragweed plants can produce three or four times more pollen due to higher carbon dioxide levels.

While this may simply amount to a nuisance for many people, the effects can be far more dangerous for vulnerable populations, like children with respiratory problems. Those whose lungs are more prone to reacting to pollen could experience more problems with asthma, which can be much more dangerous than just allergic rhinitis.

Conclusion

Elevated atmospheric levels of carbon dioxide have been shown to produce in laboratories what many people have suspected is true in the world at large: higher levels of pollen and mold spores that cause allergies. Both spring and fall hay fever seasons have been documented as being longer due to earlier thaws and later first frosts, and doctors have reported seeing more allergy sufferers in their offices in recent years. People who suffer from ordinary hay fever may want to brace themselves for longer allergy seasons in the years to come, and be prepared with medications for fighting allergy symptoms. Those with more serious problems, like asthma, should work closely with their doctors to be prepared should allergy symptoms turn dangerous.

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