Allergen Report: September 2024

Summary

September means peak ragweed season across nearly every U.S. state, with leaf mold and wildfire smoke adding to the airborne mix. Here's your region-by-region pollen breakdown and practical tips for breathing easier this fall.

In This Article

Ragweed Season Is in Full Swing·September Pollen by Region·Northeast·Southeast·Midwest·South Central·Southwest·Northwest·Opening the Windows? Check Your Air First·Leaf Mold: Fall's Sneaky Allergen·International Day of Clean Air for Blue Skies

Ragweed Season Is in Full Swing

If you've been reaching for tissues and allergy medicine lately, you're not alone. September is peak ragweed season, and unless you're lucky enough to live in Alaska (the only U.S. state where ragweed doesn't grow), there's a good chance this persistent weed is affecting your air ^[1]. What makes ragweed so relentless? A single plant can produce up to one billion pollen grains in a season, and those grains can travel more than 100 miles on the wind ^[2].

Ragweed typically blooms from late summer through early fall, ending a couple of weeks after the first frost ^[2]. So if frost hasn't hit your area yet, hang in there.

The silver lining: tree and grass pollen are winding down for the year, with just a few stragglers finishing their seasons. The not-so-silver lining: active wildfires may still be sending smoke across state lines, affecting air quality in communities far from the source fires ^[3]. There may also be an uptick in airborne fine particulate matter (PM2.5) as schools, businesses, and other industries resume normal operations after summer.

September Pollen by Region

Here's a snapshot of the typical pollens found across the United States this September [4, 5]:

Northeast

Tree pollen: Cedar, Juniper
Grass pollen: Bermuda
Weeds: Cocklebur, Dogfennel, Ragweed, Sagebrush

Southeast

Tree pollen: Cedar, Elm, Juniper
Grass pollen: Bermuda
Weeds: Cocklebur, Dogfennel, Ragweed, Sagebrush

Midwest

Tree pollen: Typically none in measurable quantity
Grass pollen: Bermuda, Johnsongrass
Weeds: Cocklebur, Marsh Elder, Nettle, Plantain, Ragweed, Russian Thistle, Sagebrush

South Central

Tree pollen: Elm
Grass pollen: Bermuda
Weeds: Cocklebur, Marsh Elder, Nettle, Plantain, Ragweed, Russian Thistle

Southwest

Tree pollen: Cedar, Elm, Juniper
Grass pollen: Typically none in measurable quantity
Weeds: Cocklebur, Ragweed, Sagebrush

Northwest

Tree pollen: Typically none in measurable quantity
Grass pollen: Typically none in measurable quantity
Weeds: Cocklebur, Ragweed, Sagebrush

Opening the Windows? Check Your Air First

With fall just around the corner, it's tempting to throw open the windows and enjoy the cooler air. We're all for it, but keep an eye on your local outdoor air quality before you do. You don't want to invite pollen, wildfire smoke, or other uninvited airborne guests inside.

If the air outside isn't exactly fresh, a high-quality air purifier can help.

Leaf Mold: Fall's Sneaky Allergen

Soon the ground will be covered in fall leaves. They may be beautiful on the trees, but once they're down and hit by a few rain showers, mold starts to grow. Mold thrives in warm, damp environments, and a pile of wet leaves is the perfect breeding ground ^[6].

For the many people sensitive to mold, this time of year can bring a familiar set of symptoms: sneezing, runny nose, itchy or watery eyes, coughing, and wheezing ^[6]. Mold exposure can also trigger asthma attacks in people who are sensitive [7, 8].

The good news? There are practical ways to protect yourself:

Wear a mask, gloves, and long sleeves when raking or working around fallen leaves to reduce exposure ^[9]
Don't let leaves pile up. Rake, bag, and dispose of them before they have a chance to decompose and become mold factories
Watch your local air quality reports for mentions of high mold spore counts
Talk to your doctor about antihistamines to help manage symptoms during peak mold season ^[6]

International Day of Clean Air for Blue Skies

September 7 marks the International Day of Clean Air for Blue Skies, designated by the United Nations General Assembly in 2019 to emphasize the need for cleaner air worldwide ^[10].

The day highlights a sobering reality: according to the World Health Organization, air pollution is the leading environmental health risk globally ^[11]. The combined effects of outdoor and household air pollution are associated with an estimated 6.7 million premature deaths each year ^[12]. A major driver? The burning of fossil fuels, which releases harmful pollutants like fine particulate matter into the atmosphere ^[13].

These effects aren't distributed equally. Women, children, and older adults in lower-income communities bear a disproportionate share of the health burden [14, 15]. And the economic toll is staggering: a World Bank report estimated the global health cost of PM2.5 air pollution at $8.1 trillion, equivalent to 6.1% of global GDP ^[16].

While an air purifier can help you manage your indoor air quality, September 7 is a great reminder to think about what you can do to improve outdoor air quality in your own community, too. Small steps add up.

References

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