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Mold and pollen can cause relatively similar respiratory symptoms, like sneezing, a runny nose, itchy and watery eyes, and wheezing in patients with asthma.  Credit: Pexels

CHICAGO — As pollen numbers dwindle, rising mold counts will usher in the second wave of allergy season, experts say.

Pollen counts in the Chicago area are typically highest from mid-August to the end of September. The peak pollen counts have already passed, Accuweather senior meteorologist Alan Reppert said. As temperatures cool, pollen counts will drop to near zero in the coming weeks. 

Once the temperatures drop below freezing for the first time — likely around mid-October — residents can stop expecting to encounter pollen outdoors, Reppert said. Mold counts, however, are not as strictly tied to temperature as pollen, he added.

“Mold really increases as we get more into the fall, and we see leaves on the ground and any rain that comes into the area,” Reppert said.

Because mold spores grow most in wet environments, the counts will be higher in the suburbs and outskirts of Chicago rather than the middle of the city, Reppert said. Areas with excess water or leaves on the ground are more likely to breed mold.

Mold and pollen cause relatively similar respiratory symptoms, according to University of Chicago Medicine Professor Christina Ciaccio. These can include sneezing, a runny nose, itchy and watery eyes, and wheezing in patients with asthma. 

To distinguish allergies from viral infections like COVID-19, Ciaccio said to keep two difference in mind: fevers, which allergies do not generally cause, and itchy eyes and noses, which are unique to allergy symptoms.

Steroid nasal sprays are the most effective allergy medication, she added. Most are available over the counter, and children under 12 years old should take one spray per nostril daily, while others can take two per nostril daily. These sprays generally take one to two weeks to become fully effective, so people can also take oral antihistamines like Claritin, Allegra, Zyrtec or Xyzal for more immediate relief, Ciaccio said.

Ahead of the holiday season, Ciaccio said residents should also be wary of “Christmas trees asthma,” when bringing a tree inside the house before the frost can trigger mold allergy symptoms.

“If you’re allergic to mold, we’ve also seen a lot of reactions around pumpkin patches,” Ciaccio added. “So it may be wise to pre-medicate with some antihistamines before you go apple picking or pick pumpkins during the fall season.”


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