Fall Allergies: Common Causes and What You Can Do

Published August 16th, 2021 by Bridget Reed
Fact Checked by
Chris Riley
Medically Reviewed:
Erik Rivera

If you suffer from fall allergies, you’re not alone. Despite the fact that most people consider spring to be the biggest season for allergy symptoms, many people also experience allergy symptoms in the fall. There are several common causes of fall allergies.

Common Causes of Fall Allergies

Experiencing allergy symptoms in the fall can be especially frustrating because most people commonly associate seasonal allergies with the blooming of flowers in the spring. However, fall allergies are very common, particularly in people with spring allergies.


Ragweed is by far the number one cause of fall allergies. This common weed grows throughout the United States but is particularly common in rural parts of the East and Midwest.

Even if you don’t live near ragweed, you can still be affected by it, as just one ragweed plant can produce up to one billion pollen grains in a given season. These pollen grains can travel quite far, which means you don’t have to live close to ragweed to feel its effects. Ragweed pollen has been found in the air up to 400 miles out to sea and two miles high.

Ragweed commonly blooms beginning in mid-August as the nights start to get longer. During this time, the ragweed starts to flower and produce pollen. The plant continues to flower until the first frost, which means you could be suffering from allergies for months, depending on where you live.

An estimated 15 percent of Americans experience allergy symptoms from an allergy to ragweed, which means those people are in for a long autumn if no treatment is used. Up to 75 percent of people who experience allergies in the spring are also allergic to ragweed, which means they will have symptoms in both spring and fall.

Mold and Mildew

Mold and mildew are other common fall allergens. While mold and mildew can be present year-round, particularly in indoor areas, they often become worse in the fall due to the presence of damp fallen leaves raked into compost piles or left to litter the ground.

Mold and mildew are attracted to moist, warm areas, and while the weather cools off in the fall, these compost piles and leaf piles generate heat. As a result, mold and mildew can release more spores and spread more rapidly in the fall before becoming dormant in the winter.

People with allergies to mold and mildew can experience symptoms resulting from outdoor exposure to mold as well as indoor exposure, as mold commonly grows in damp indoor areas such as under the kitchen sink, inside the bathroom, and in the basement.

Dust Mites

Many people think they are allergic to dust, but they’re actually allergic to dust mites. Dust mites are tiny insects that feed on the flakes of human skin that shed naturally throughout the day and are present in your home no matter how often you clean.

These microscopic creatures are most commonly found in temperatures ranging from the high 60s to the mid-70s, which are common fall temperatures. They can also be found at room temperature, so they thrive year-round, although there may be an increase in dust mite populations during the fall. Dust mites die off when humidity dips below 70 percent and in extreme cold.

Pet Dander

Another common cause of fall allergies is pet dander and fur. Pet dander consists of the microscopic particles of skin that are naturally shed by animals. It can easily build up indoors and increase during the fall and spring, as animal coats typically shed during these seasons to prepare for winter and summer.

People with seasonal allergies are more likely to have allergies to their pets as well, with 40 percent of people with seasonal allergies experiencing pet allergies as well.

While people can be allergic to any type of pet, some animals are more likely to cause allergic reactions than others. People are twice as likely to be allergic to cats as they are to be allergic to dogs. Certain breeds of dogs, including bulldogs and Saint Bernards, are more likely to cause an allergic reaction than other breeds. However, everyone experiences pet allergies differently and some people may find that they are allergic to some breeds but not others.

Treating Fall Allergies

Once you are experiencing fall allergy symptoms, you may need medication in order to bring your symptoms under control. Fortunately, there are lots of different over-the-counter medications and prescription drugs that are designed to treat seasonal allergy symptoms.

Allergy medications for seasonal allergies typically fall into one of three categories when purchased over the counter, including antihistamines, decongestants, and corticosteroids. Antihistamines and decongestants are fast-acting medications that are most helpful for the treatment of acute symptoms and are often used on a short-term basis, while corticosteroids take two to four weeks to start working and are generally intended for long-term use.

  • Antihistamines include medications like diphenhydramine (Benadryl) and work by blocking the action of a chemical called histamine in the body that is known to cause allergy symptoms. Common side effects of antihistamines include drowsiness.
  • Decongestants include oral medications like pseudoephedrine (Sudafed) and work by narrowing the blood vessels that line the nasal passages, which decreases congestion and helps you breathe more easily. Nasal decongestants work quickly but cannot be used for more than three days due to their potential to cause a rebound effect.
  • Corticosteroids include medications like fluticasone (Flonase) and work by reducing inflammation in the tissues that line the nasal passages. These medications can take up to two to four weeks to start working and are best when taken every day for an extended period of time in order to manage allergy symptoms.

Preventing Fall Allergies

If you experience fall allergies, you know how unbearable those symptoms can be. Fortunately, there are some steps you can take to minimize your experience with fall allergies depending on the type of allergies you have.


As noted above, ragweed is tough to avoid because the pollen can travel for long distances even if you do not live in an area where ragweed is common. As a result, the best course of action is to keep up to date on your local pollen count by checking your local news reports and weather apps.

Try to avoid going outside as much as possible during days when the pollen count is especially high, and wear a mask when you do go outdoors. Pollen counts are typically highest during the hottest part of the day (mid-morning through mid-afternoon).

Indoors, make sure you clean your home regularly and avoid letting pollen inside. Keep your doors and windows shut during ragweed season and remove articles of clothing, such as your jacket or shoes, before entering your house to avoid bringing the pollen inside. Make sure to wash and clean your home regularly and don’t dry your clothes outside. Outdoor pets should be bathed frequently, particularly if you are bringing them inside the house at night.

Mold and Mildew

Because mold and mildew are known to increase during the fall by spreading to piles of leaves, keep up with your raking during the fall season and bag leaves so you can dispose of them quickly. Wear a mask while raking or removing leaves from gutters.

If you have a compost pile, make sure to keep it far from the house. Indoors, you can consider using a dehumidifier in areas of high humidity, such as bathrooms and kitchens, to minimize mold and mildew buildup.

Dust Mites

It’s unlikely you’ll ever be able to get your home completely free of dust mites, and even if you do, they are likely to come back.

However, it is possible to manage the number of dust mites in your home. As the weather gets cooler, use this time to clean your air vents before you use your heating system for the first time. Consider using dust-proof covers for your mattress and pillows, and regularly wash your bedding in hot water. Keeping your humidity level low with a humidifier can help, as can regularly vacuuming and dusting.

People with severe allergies to dust mites may need to remove carpeting and rugs from their homes and replace these areas with hardwood.

Pet Dander and Fur

Some people with pet allergies may not be able to have pets in their home. However, some breeds, such as Poodles, Havanese, and Schnauzers are considered hypoallergenic and may be ok for some individuals.

 If you have allergies, try to minimize your contact with animals you are allergic to. People with allergies who are able to have pets might consider keeping pets only in certain areas of the home, using a strong air purifier, keeping the pets off the furniture, and regularly bathing their pets.


The most common causes of fall allergies are ragweed, mold and mildew, dust mites, and pet dander and fur. If you experience fall allergies, you may be able to treat your symptoms by using allergy medications like antihistamines, decongestants, or corticosteroids. 

However, it’s also important to limit your exposure to these allergens by keeping your home extra clean, keeping humidity levels low indoors, and avoiding going outside as much as possible on high pollen days.


Ragweed Pollen Allergy | Asthma and Allergy Foundation of America

Four Things You Might Not Know About Fall Allergies | American College of Allergy, Asthma, and Immunology

Dust Mites | American Lung Association

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