In this section: Asthma Triggers | Indoor Triggers | Outdoor Triggers | Occupational Asthma | Pets & Animals

Indoor Triggers

With smog, pollen and severe weather changes, you might think that you’re more likely to encounter more triggers outdoors than indoors. In fact, the opposite is true. Canadians spend 90% of their time indoors. This, along with changes in how our homes are built, is has lead to poor indoor air quality and more triggers, in our homes.

Fortunately, a great deal has been learned about asthma triggers that exist inside. By educating yourself about indoor hazards, you’ll discover simple ways to reduce their levels.

Dust & Asthma

Dust mites are a common allergic trigger for people with asthma.

Dust mites are tiny insects that live in carpet fibres, plush furniture, curtains, mattresses, pillows, and bedding. They congregate in soft-surfaced places where there is an abundant food supply. They eat flakes of skin and reproduce in warm and humid environments. The excretions and body parts of these tiny, spider-like creatures can be a powerful trigger of asthma symptoms.

Minimize Your Risk

Effective strategies for minimizing dust mites are:

  • Use a dehumidifier in damp area. Keep the humidity level below 50 %. Dust mites can’t survive in dry environments.
  • Remove carpets, especially in the bedroom.
  • Launder bed linens in very hot water (55 degrees Celsius).
  • Encase your pillow, mattress and box spring in mite-allergen impermeable encasings.

Cockroaches & Asthma

Cockroaches are one of most hated household pests, and for good reason. Not only are they a terrible nuisance, their feces have been shown to trigger symptoms in individuals with asthma.

If your home has cockroaches, make sure that food and water are never left where they can get at them. To ensure they leave and never come back, call a professional exterminator.

Mould & Asthma

Moulds are fungus that can be found just about anywhere it’s damp and where air flow is minimal, like basements and bathrooms. Their airborne spores can trigger asthma symptoms, but there are many ways to avoid them. The best way is to keep your home dry and clean.

Minimize Your Risk

  • Monitor the humidity level in your home with a hygrometer and keep the level between 40-45%.
  • Make sure your home is well ventilated.
  • Remove carpeting where possible. If carpet is kept, vacuum thoroughly and frequently using a vacuum cleaner with a HEPA filter.
  • Clean moldy areas, especially in bathrooms, with an anti-mould cleaner like vinegar or a chlorine-bleach solution. When using these chemical, be sure to use them in a well ventilated area.
  • Ensure that you have proper drainage around your house.
  • Use a dehumidifier if humidity is higher than 50% (basements).
  • Always use bathrooms and the kitchen fans.
  • Reduce the number of your house plants.
  • Do not have carpet in bathrooms or directly on concrete floors in the basement.

Chemicals & Scented Products

Asthma attacks can be triggered by exposure to chemical fumes (such as laundry detergents, cleaning products, hairspray, scented cosmetics, perfume, paints, etc). Many people with asthma are affected by airborne chemicals and fragrances. They may be exposed to them in the home, or even at work.

At home, chemicals and fragrances are reasonably easy to control. If you have paints or other volatile products in your house, you can get rid of them or seal them carefully and place them in a garage or shed. If you’re sensitive to heavy perfumes, try not to use products that use them.

Laundry detergent is an often unrecognized source of asthma triggers. Most laundry detergents contain high concentrations of irritating fragrances. Try to use only all-natural, unscented and avoid the use of dryer sheets which can be heavily doused in synthetic fragrance.


Exposure to smoke of any kind can be harmful and trigger asthma symptoms. Everyone knows that smoking isn’t healthy, but if you have asthma it can be even more dangerous. Smoke is frequently responsible for the onset of asthma symptoms and attacks and must be avoided. Tobacco smoke, even second-hand or thirdhand, can trigger asthma symptoms. If you have asthma, do not allow any smoking in your home, your car or anywhere else where you spend a lot of time.

Second-hand smoke is especially harmful for children with asthma because their lungs are still developing. Children exposed to second-hand smoke are more likely to experience asthma attacks and to have more severe symptoms. It is also critical that pregnant women avoid smoking and second-hand smoke, as exposure during pregnancy increases the likelihood of children developing asthma.

Third hand smoke (i.e., smoke lingering on clothing or car seats) can also irritate the airways and worsen asthma symptoms.

If you or your child has asthma and you smoke, talk to your doctor about how to quit. If you do not smoke, recognize that second-hand smoke & third hand smoke, should be avoided at all times. If you wish to quit smoking, there are many options available to assist you. Talk to healthcare provider about how nicotine-replacement therapy, counseling and other treatments can help you butt out for good.

Marijuana smoke contains many of the same harmful chemicals as tobacco smoke. Long-term marijuana smoking has been associated with increased coughing, sputum (phlegm) production and wheezing. Smoking marijuana can make existing lung conditions worse. If you have asthma, marijuana smoke can cause an asthma attack leading to hospitalization or even death (American Thoracic Society).

Pets & Asthma

Many types of common household pets can be allergic asthma triggers. People with pet allergies are mainly allergic to the animal’s dander (flakes of shed skin), saliva, and urine. These pet allergens are very small particles and are in the air even if the animal is present. Even if you choose to move your pet to a new loving home, the allergens can remain for months on furniture and in carpets. Animals can also carry pollen and mould into the house from the outdoors on their fur.

If you have asthma and a pet allergy, reducing expose to pet allergens is the most effective way to help your asthma symptoms. If you don’t already have a pet, don’t get one if you asthma and a known pet allergy. If you have a pet and a pet allergy, consider finding a new loving home for your pet.

You can learn more about living with asthma and pets here.

Viral Infections & Asthma

Viruses can both cause asthma episodes and make people with asthma more sensitive to other asthma triggers.

Viral triggers include:

  • The rhinovirus (common cold)
  • Respiratory syncytial virus (RSV)
  • Certain flu viruses

Your healthcare team can tell you about ways to avoid viral infections, and what to do when you get sick.

People with asthma are encouraged to get the flu shot in the Fall.

Asthma & Allergy HelpLine

Do you have questions about asthma? Contact our free helpline service to be connected with a Certified Respiratory Educator who can provide you with personalized support.

Pets & Animals

Pets and other animals can be allergic asthma triggers. Learn about what you can do to live your pets and manage your asthma. Know your triggers and stay healthy.

Breathe Easy: Triggers

Download a copy of our Breathe Easy Booklet Series on asthma triggers. It provides useful information on managing your asthma, avoiding triggers and staying symptom-free . [Click here to download in French].