Reviewed by: HU Medical Review Board | Last reviewed: September 2021

Allergens are common triggers of asthma symptoms for children and adults. Asthma triggered by allergies is called allergic asthma. Common allergens include:1-7

  • Pet dander
  • Pollen (grass, trees, weeds)
  • Dust mites
  • Insects
  • Rodents
  • Mold

Allergens that cause a reaction for you may not affect other people.

It is important to know what allergens trigger your asthma. Avoiding exposure to your allergens may reduce your asthma symptoms. This can help lower the amount of asthma drugs you need.

Why can allergies trigger asthma?

An allergic reaction happens when your body thinks a foreign substance is a threat. Allergens can enter the body by inhalation, swallowing, or touch. After exposure to an allergen, your body recognizes it as foreign and tries to get rid of it. Your immune system tries to protect you by releasing a chemical called immunoglobulin E (IgE).1

High amounts of IgE can trigger inflammation by activating special allergy cells in the body. This can lead to increased swelling of the airways and cause your airways to narrow, making it hard for you to breathe. For some people, this leads to symptoms of asthma.1

How common is allergic asthma?

Allergic asthma is the most common type of asthma. About 25 million people in the United States have asthma. Around 60 percent of people with asthma have symptoms triggered by allergies.1,2

What are some allergens that trigger asthma?

Pet dander

Dander refers to flakes of dried skin, glands, and saliva from household pets. Dander from cats and dogs trigger allergies for many people. Between 25 and 50 percent of children with asthma are sensitive to pet dander.3

Pet dander is even present in homes and schools without pets. Pet dander allergens remain in the air for a while before settling down. This means they can be carried by people to environments without a pet.3

Ways to reduce the impact of your pet on your asthma include:3,4

  • Keeping pets out of your bedroom
  • Grooming and bathing them often
  • Using a vacuum and air cleaner with a HEPA filter
  • Using allergen-proof bedding
  • Feeding specialized cat food that reduces their allergen

If dander is still triggering your asthma symptoms, you may want to find the pet another home. It may take several months for allergens to go away after moving a pet. Talk to your veterinarian about finding them a new home. Also ask them about misconceptions about pet dander allergies. For example, “non-allergenic/hypo-allergenic” or short-hair pets may not reduce your sensitivity. This is because the allergen mostly comes from the skin and saliva.3

Dust mites

Dust mites are tiny pests that live in soft surfaces, such as carpets and furniture coverings. The mites and their feces can be allergens. Dust mites live on skin flakes and need moisture to grow. Dust mite allergens do not stay in the air for a long time. This means they are usually not present in undisturbed air.3,5

One out of every 2 to 3 children with asthma are sensitive to dust mites. It is also hard to completely avoid dust mites, unless you live in a very dry climate. There are ways to reduce your exposure to dust mites, including:3-5

  • Using dust-proof bedding
  • Washing your bedding weekly in hot water and drying completely
  • Vacuuming carpets and rugs often
  • Removing carpets and drapes from bedrooms
  • Removing soft objects like stuffed toys from the bedroom
  • Keeping humidity levels low with a dehumidifier, ideally at 30 to 50 percent
  • Having other people dust and vacuum your home
  • Wearing a face mask while cleaning your home


Mold produces spores that get into the air and trigger asthma. It is usually found in moist places, such as basements and bathrooms. About half of children with asthma are sensitive to mold. About half of homes have enough mold to trigger asthma symptoms.3

Ways to reduce exposure to mold in your home include:4

  • Drying wet items quickly to prevent mold growth
  • Fixing water leaks
  • Replacing absorbent materials if mold is present
  • Using a dehumidifier to maintain low humidity
  • Running the exhaust fan in the bathroom when showering


Pollen is the powdery substance that comes from plants that is spread by the wind. Grass and weed pollen are the most common types that trigger allergic asthma. Some pollen allergies are seasonal. This means they flare up at a certain time of year. In the spring, trees release their pollen. In the summer, grass releases their pollen. In the fall, weeds are the issue. Allergens like dust and pets cause symptoms year-round.1,2


Cockroaches are pests found in homes and other buildings. The saliva, feces, and other body parts of cockroaches can trigger asthma. They are attracted to food and water and hide in tight spaces. Cockroaches are very common in urban homes and buildings. Between 60 and 80 percent of children in cities with asthma are sensitive to cockroach allergens.3,6

Tips to reduce exposure to cockroaches include:4,6

  • Clean dishes, crumbs, and spills immediately
  • Keep food out of the bedroom
  • Store food in airtight containers
  • Keep trash in a closed container
  • Keep counters, tables, and floors free of clutter
  • Seal cracks or openings in cabinets and walls
  • Use traps in areas away from children and pets
  • Avoid using sprays, which may also cause asthma attacks
  • Consider hiring an exterminator


Research shows that rodent urine, saliva, and skin can trigger asthma symptoms. Mouse allergens are found in 75 to 80 percent of U.S. homes, and concentrations in inner-city homes are as much as 1000 times higher than those found in suburban homes. Exposure to mouse allergen has been linked to uncontrolled and more severe asthma in children, especially those who live in cities.7

Tips to reduce exposure to rodents include:7

  • Seal holes and cracks in foundations and joints with copper or stainless steel mesh
  • Add rodent barriers to foundation walls
  • Close off passages through interior floors, walls, and ceilings
  • Keep plants and trees at least 3 feet from your home
  • Put trash in covered garbage cans and dumpsters
  • Store food in rodent-proof containers

By providing your email address, you are agreeing to our privacy policy.