• Fall allergies are often caused by weeds like ragweed. 
• Fall allergy symptoms can include a runny nose, nasal congestion, sneezing, or itchy eyes. 
• To treat your fall allergies, you should start taking allergy medication at the beginning of September. 
• This article was medically reviewed by Omid Mehdizadeh, MD, otolaryngologist and laryngologist at the Pacific Neuroscience Institute’s Pacific Eye, Ear & Skull Base Center at Providence Saint John’s Health Center in Santa Monica, CA
• This story is part of Insider’s guide on seasonal allergies.

In the US, indoor and outdoor allergies affect over 20 million adults and six million children annually, according to the Asthma and Allergy Foundation of America. 

While spring is generally considered the worst allergy season, the fall also brings allergy irritation for many people. This is because some plants don’t produce much pollen in the spring or summer, and instead reach their highest pollen counts in the fall. 

Here’s what you need to know about the major causes of fall allergies and how to treat your allergy symptoms. 

What causes fall allergies? 

Often, the areas with the worst fall allergies experience four distinct seasons and long autumns, like most parts of the midwest and east coast, says Mahboobeh Mahdavinia, MD, an associate professor of allergy and immunology at Rush University Medical Center. 

During the fall, the following pollen sources and irritants are most likely to cause allergies: 

Weeds 

The pollen from ragweed causes allergies in over 23 million people each year, according to the American College of Allergy, Asthma, and Immunology. Pollen counts reach their highest levels in mid-September, and the wind can blow pollen over 700 miles. 

As a result, ragweeds are a particularly disruptive fall allergen. They’re a hardy soft-stemmed plant with 17 species in North America, concentrating in the eastern and midwestern US.

Common species of ragweeds include: 

• Sunflowers
• Goldenrods
• Marigolds
• Sage
• Zinnias
• Rabbit brush
• Burweed marsh elder

“Classically, we talk about trees being springtime, grass in the summertime, and weeds in the fall,” says Matthew Ellison, MD, an assistant professor of head and neck surgery at Duke University. “And that can be any weed. So some parts of the country don’t have ragweed, but there are other weeds that pollinate in the fall.” 

Other common weeds that can cause fall allergies include:

• Pigweed
• Lambs quarters
• Wormwood

Grasses

Grasses release small, light pollen that the wind can carry for hundreds of miles, according to the Asthma and Allergy Foundation of America. 

Ellison notes that in warmer regions of the US like the South, grasses can trigger allergies because they continue to pollinate in the temperate autumns and winters of these seasons. 

Common grasses that cause fall allergies in temperate regions include: 

• Bentgrass
• Bluegrass
• Ryegrass

Mold

Mold is another common trigger for fall allergies. Indoor molds grow in moist places, such as leaky roofs, windows, and pipes, according to the Center for Disease Control and Prevention. Mold can also grow on wood, wallpaper, insulation, carpet, drywall, fabric, and upholstery. 

Outdoor mold can also exacerbate allergies, especially in the fall. Autumn causes the leaves to fall from trees, and mold grows on the decomposing plant matter. Those allergic to mold may experience allergy symptoms while raking leaves, as disturbing the decomposing plant matter can send mold spores into the air and up the nose. 

The American College of Allergy, Asthma & Immunology suggests wearing a face mask, such as the N95 mask, when raking leaves, gardening, or mowing the lawn to prevent mold spores from triggering allergies. 

Fall allergy symptoms 

Pollen from grass, weeds, and mold spores can irritate the nose and cause allergic rhinitis, which is also called hay fever. 

Symptoms of allergic rhinitis include: 

• Runny nose
• Clear mucus discharging from the nose
• Nasal congestion
• Watery, itchy, irritated eyes
• Sneezing
• Headaches
• Itchy throat
• Rashes
• Hives

How to treat fall allergies 

There are several pillars to treating seasonal allergies, says Ellison. These include: 

• Avoidance. If possible, avoid going outdoors as much as possible during the fall season if you’re triggered by plants that pollinate in the fall. Ellison says that if you do go outside, you should take a shower to wash off any pollen and reduce the chance of carrying allergens indoors. 
• Medication. Antihistamines like Claritin or Zyrtec help block the body’s allergy response, relieving symptoms such as a runny nose, itchy eyes, and sinus decongestion. Nasal sprays like Flonase can also provide relief for nasal congestion or a stuffy nose. 
• Allergy immunotherapy. These are allergy shots or allergy drops. They’re a long-term solution for allergy symptoms, but they may not be right for everyone. For more information, read about whether allergy shots are worth it for you. 
• Surgery. Ellison says surgeries, like septoplasty, can help those who don’t get relief from medication. These surgeries can help people breathe better. 

There are also many natural remedies for allergies that can help relieve your symptoms. Ellison suggests trying saline washes or spray, which is a salt-based solution designed to clear away mucus from the nasal passages and moisturize the area. 

A 2018 study published in The Cochrane Database of Systematic Reviews found that saline sprays can help alleviate allergic rhinitis in adults and children, when compared to those not using saline sprays. 

Another study found that daily saline nasal irrigation shows no adverse side effects. However, Ellison says to avoid saline nasal sprays with added decongestants like Afrin or Neosynephrine, as decongestants can be habit-forming and harmful for your sinuses. 

Ellison doesn’t recommend herbal or homeopathic remedies because there’s not as much clinical data supporting their efficacy. Overall, Mahdavinia says treating fall allergies with antihistamines is best practice. 

“Taking daily non-sedating antihistamines is usually the first line,” Mahdavinia says. “But those with more intense symptoms need to be treated with intranasal medications. They [allergy treatments] are best to be started ahead of the allergens peak to be most effective.” 

Takeaways 

If you know you have seasonal fall allergies, you should consider starting allergy treatment at the beginning of September. This will make your treatment more effective and help reduce the severity of your symptoms if they occur. 

Your fall allergies from outdoor allergens should subside as winter approaches, and morning temperatures start to get below 50 degrees Fahrenheit. However, mold can remain prevalent until there is frost, Mahdavinia says.

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