woman sneezing with fall allergies
woman sneezing with fall allergies

What Causes Fall Allergies?

7 min read



The autumn months have their own ensemble of allergens that can trigger uncomfortable symptoms for countless individuals. From sneezing fits and itchy eyes to headaches, sinus pain, and nasal congestion, fall allergies can put a damper on the season for those affected.

Today, we’re exploring what causes fall allergies, how early they actually start, and how fall allergies may vary from region to region. Knowing what causes allergies in the fall is the first step you can take to prepare yourself for the season ahead.

Can You Get Allergies in the Fall?

One of the most common questions we hear is, “Can you get allergies in the fall?” Unfortunately, the answer is yes. Even though they’re most frequently talked about for the spring, fall allergies can be just as prevalent for many.

Allergies are the result of an overactive immune response to normally harmless substances called allergens. When an allergic individual comes into contact with these allergens, their immune system perceives them as threats and produces antibodies to fight them off.

What causes fall allergies mostly include pollen from various plants, mold spores, and dust mites. The most common fall allergen is ragweed pollen, notorious for causing sneezing, a runny nose, and itchy throat.

When Do Fall Allergies Start?

As you learn more about what causes fall allergies, you may be surprised to learn fall allergies typically start in late summer and extend into the autumn season. While the exact timing may vary depending on factors such as geographic location and local climate, fall allergies often begin as early as August and can persist until November or even December.

As the days become shorter and the weather cools down, certain allergens become more prevalent, triggering allergic reactions in susceptible individuals.

What Causes Fall Allergies? A Look at Common Allergens

So, what causes fall allergies exactly? Several allergens are responsible for triggering fall allergies.

Ragweed: The Most Common Fall Allergen

The most prevalent among what causes fall allergies is ragweed, a flowering plant that releases vast amounts of pollen into the air during the fall season. An estimated 75% of people allergic to spring plant pollen will also be allergic to ragweed. Even if ragweed doesn’t grow in your immediate area, the pollen is lightweight and can be easily carried by the wind over 50 miles, leading to widespread allergy symptoms.

As you learn what causes allergies in the fall and more about ragweed, you also learn that pollen levels are not the same throughout the day. In fact, ragweed pollen levels tend to be worse during the morning hours. This can help you plan your day around peak pollen level hours and avoid discomfort as much as possible.

It’s also common to experience Pollen Food Allergy Syndrome with ragweed and certain other allergens, which you can learn more about here: “What is Pollen Food Allergy Syndrome?

Other Common Fall Allergens

What causes fall allergies isn’t limited to ragweed. There are numerous other common allergens that may have you sneezing, coughing, or experiencing a runny nose this season.

  • Mold spores: Damp and decaying vegetation in the fall provides an ideal environment for mold growth. Mold spores become airborne and can trigger allergic reactions when inhaled. For outdoor mold, try to avoid areas it may manifest such as piles of wet leaves. For indoor mold, use a dehumidifier to keep the humidity levels below 45%.
  • Dust mites: Dust mites are tiny, microscopic creatures that feed off of the moisture in the air. They can be found in bedding, upholstery, and carpeting. They’re also prevalent in schools, making them a common culprit for what causes fall allergies in children. To help with dust mites indoors, wash your sheets in hot water weekly, vacuum weekly,  and keep the humidity levels under 50% using a dehumidifier. Dust mite allergies are present year-round, but because we begin to spend more time indoors in the fall, our symptoms may become more bothersome. A telltale sign of dust mite allergy is symptoms first thing in the morning, as dust mites may be living in your bedding.
  • Pollen from other weeds: Besides ragweed, other weed species like lambs quarters (part of the goosefoot family), pigweed, and sagebrush can release pollen during the fall, triggering allergic reactions.
  • Pet allergens: Pet dander and saliva, can become airborne and cause allergies in susceptible individuals. During the fall, when people spend more time indoors with their pets, exposure to pet allergens may increase. Keeping your pet out of the bedroom, washing it once a week, and using an air filter can help reduce the amount of pet allergen in your home.

Learn more about how to reduce allergies at home and find a solution to your pet allergy after you finish this article.

Do Fall Allergies Differ By Region?

The severity of fall allergies can vary from region to region. Several factors contribute to this, including the types of allergens present, local climate, vegetation, and air quality.

Generally, the regions with the worst fall allergies are those with a high concentration of specific allergens and environmental conditions that facilitate higher levels of dispersion such as wind, heavy rainfall, or pollution.

Fall Allergies By Region in the United States

Northeastern region: The Northeastern states are known for having some of the worst fall allergies. Ragweed is particularly prevalent in these areas, releasing large amounts of pollen during the fall season. Additionally, mold spores and pollen from other weeds contribute to the high allergen levels in the area.

Midwestern region: The Midwest region can also experience severe fall allergies. Ragweed is common in this area, along with other pollen like that from Marsh Elder and Russian thistle.

Southeastern region: The Southeastern region of the country has an extended growing season and higher humidity levels, which can contribute to what causes fall allergies. Ragweed, along with other local weed pollen like sagebrush and pigweed frequently trigger allergies in this area. You may also find allergens from warm-season grasses like Bermuda Grass or Bahia Grass.

Southwestern region: The Southwest region doesn’t escape what causes fall allergies either. Ragweed is less prevalent in this region, but other regional weed pollen like sagebrush and mold spores can still cause allergic reactions. Luckily, in arid regions and those at high altitudes the relative humidity levels are low, so indoor mold and dust mites cannot thrive.

West Coast: Above-average rainfall has been bringing worse fall allergies to the west coast, with the proliferation of ragweed and other weed pollens as well as outdoor mold spores.

So, can you get allergies in the fall? The answer is a resounding yes. In fact, what causes allergies in the fall may in fact start during the late summer and continue through the autumn months. The first step to a comfortable fall is identifying your allergies. Our indoor and outdoor at-home allergy test can help you learn how best to prepare for the season ahead.

Keep Learning

They say knowledge is power. We couldn’t agree more. Learn about the chronic health condition that affects 50 million Americans every year.