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Each person has their own set of asthma triggers. It is important to try to determine your set of triggers so that you can work towards eliminating or reducing them. Click on the list of common asthma triggers below for more information.

Asthma and allergens

Allergens only affect people who are "sensitized" to them, which means their immune system (the body's defence system) is "primed" and ready to react to the allergen. To determine which allergens affect you, your doctor will assess your symptoms and send you for an allergy skin test. Allergens include:

      • Pet allergens (eg., cats, dogs, hamsters, birds, etc.)

      • Dust mites

      • Pollen

      • Mould

      • Sometimes foods and food additives

Asthma and Pet Allergens

Pets shed tiny bits of skin (dander). Cats and dogs are common allergens, but many different animals can cause allergies. Other allergens from pets include cat saliva and urine from animals such as hamsters, gerbils and rabbits.

If someone is allergic to a pet, the best measure by far is to find another home for the pet. If this is not possible, there are some ways you can try to reduce exposure:

      • Keep the pet out of the bedroom, limit it to certain areas of the home and keep it off furniture

      • Have your pet washed and brushed frequently - by someone who is not allergic

      • Another family member should feed and care for the pet

      • Encase mattress and pillows in allergy-proof covers

      • Reduce carpeting and buy furniture with leather or vinyl coverings that may reduce the absorption of allergens

      • Don’t replace the pet once it is gone

If you don't have a pet but intend to visit someone who does, you may want to use medications to prevent or relieve symptoms of asthma and allergies. When you do visit, you might want to ask that the pet be kept out of the room you are in. However, if you are very sensitive to pet allergens, you will likely need to stay away from any homes with pets. Try to arrange to meet somewhere else.

If you do have a pet but are not sure if it affects your asthma, ask yourself this: when you leave home on a holiday without the pet, does your asthma improve?


Asthma and Dust Mites

Dust mites are tiny microscopic insects that feed on skin particles that humans shed. They thrive in warm, moist places with lots of human skin: mattresses, pillows, carpet, and bedding. People with dust allergies are allergic to the droppings (feces) of dust mites. To get rid of the allergy-causing droppings, you must wash out the existing droppings and kill the mites so they don't make more droppings.

The following measures may help:

      • Encase your mattress and pillows with special allergen-proof covers, or with plastic or vinyl covers. Tape the zipper for a complete seal.

      • Keep the humidity in your home below 50% - dust mites can’t survive well in low humidity

      • If possible, remove carpets, rugs, and heavy curtains especially from your bedroom but also from the rest of the home

      • Keep your bedroom free of clutter - books, boxes, and clothes lying around can all collect dust

      • Minimize the number of stuffed toys in a bedroom, as these can collect dust, and make sure they are washable

      • Vacuum rugs and carpets at least once a week

      • Wash your bedding in hot water and dry it in a hot dryer every week

      • Dust every week with a damp cloth

Asthma and Pollen

The pollen grain transports the male reproduction part of a plant to the female part for the purpose of growing a new plant. Wind-pollinated plants are of most concern to people with allergies since they are transported by the wind and are therefore readily inhaled into the nose and lungs.

Typical pollen seasons:

      • Tree pollen in the spring

      • Grass pollen in early summer

      • Ragweed and other weeds August until the first frost


What can you do:

      • Keep windows closed in home and car - use an air conditioner if needed

      • Some people may need to avoid going outside when the pollen levels are high - check pollen reports

      • Check the pollen counts in your area to see when the pollen you're allergic to is at a high level

      • If possible, people with allergies to pollen and mould should not cut the lawn

      • If you've been outside when there is a lot of pollen, take a shower to wash the pollen from your skin and hair and change into new clothes when you come indoors 

Asthma and Mould

Mould can grow indoors all year in damp basements and bathrooms, and outdoors from spring to fall. Mould cannot grow without moisture.

What can you do:

      • Keep the humidity in your home to less than 50 per cent - you can buy a hygrometer to measure humidity at local hardware stores

      • Moulds don’t like air flow, so keep your basement clutter free so that air can move around

      • Always use the bathroom fan or open windows after a bath or shower

      • Use a dehumidifier in your basement if it is damp

      • Get helpful tips on controlling moisture in the home:

        The Lung Association Mould Fact Sheet

        CMHC: A Guide to Fixing Your Damp Basement

        Health Canada Resources

Asthma and Foods/Food Additives

Although it is uncommon, asthma may flare up as a result of generalized allergic reactions to food. If you're allergic to a food, you'll usually know it soon after eating it. The advantage to that is you can pinpoint the food allergy right away, especially if you've had a similar reaction before.

Foods that cause asthma symptoms in some people (usually young children) include:

      • Nuts and peanuts

      • Milk

      • Shellfish and fish

      • Eggs

      • Soy

      • Wheat

      • Food additives such as sulphites (food preservative)

Once you have had an allergic reaction to a food, the best treatment is prevention: don't eat that food! Sometimes that is difficult if you're eating prepared food and don't know what it contains. Reactions can occur to even tiny amounts.

Similar reactions can also occur after eating or drinking foods containing additives or preservatives such as sulphites found in beer, wine, dried fruit, frozen seafood and sometimes salad bars. Treatment for these reactions is the same as for a true allergic response.

Asthma and irritants  

Common asthma irritants include:

      • Tobacco smoke

      • Air pollution

      • Cold air

      • Perfumes and strong odours

Asthma and Tobacco Smoke

Smoke hangs around long after the cigarette is out, and the leftover smoke can make asthma worse.

Smoke gets in people's clothes and hair, in fabric, in furniture, in walls, in stuffed animals. Smoke can't be cleared out of a room by just opening a window or smoking near a fan.

Smoke that's trapped in all these places continues to make asthma worse, even after the cigarette is put out.

      • If you do smoke, try to quit. Call The Lung Association Lung Health Information Line at 1-888-344-LUNG (5864) or the Canadian Cancer Society’s Smokers’ Helpline at 1-877-513-5333.

      • Avoid second-hand smoke: make your home & car smoke-free and avoid places that allow smoking. 

Asthma and Air Pollution

Outdoor air pollution comes from many sources, including cars and industry. The highest pollution levels tend to be in the hot, humid days of summer. Sensitive individuals may feel health effects sooner than most, and before a smog advisory is issued.

The Lung Association advises the following:

      • Reduce outdoor activity and keep car and home windows closed when pollution levels are high.

      • Stay inside in a cool and clean environment during periods of high air pollution.

      • Follow the Air Quality Index in your area:

      • If breathing becomes difficult, contact your doctor, health care provider or go to the nearest hospital emergency department. 

Asthma and Cold Air

Cold air, especially cold, dry air, can cause asthma symptoms in some people. Exercising in cold air can also lead to symptoms. Keep your asthma well controlled so that triggers such as cold air will be less likely to bother you. The following tips may help:

      • Drape a scarf loosely over your nose and mouth to warm and humidify the air before you breathe it in. You could also buy a cold-weather face mask made for this purpose.

      • Breathe through your nose. Your nose can warm and humidify the air.

      • If your doctor recommends it, take a puff of your blue reliever inhaler (short-acting bronchodilator) before you go outside.

      • If it’s really cold outside, you may wish to exercise indoors.

      • Keep your reliever puffer with you at all times. 

Asthma and Perfumes/Strong Odours

Some people get asthma symptoms from products that have strong scents or odours. Examples include:

      • Cleaning products, including carpet and window cleaners

      • Paint fumes

      • Perfumes

      • Fabric softeners

      • Air fresheners 

      • Detergents 

      • Bleach 

      • Dry cleaning fluid 

      • Turpentine or paint thinners 

      • Paint stripper 

      • Pesticides

Depending on what makes your asthma worse, the following steps may help:

      • Use scent-free and low-odour products when possible.

      • Paint indoors at a time when you can leave the windows open or when the person with asthma is away.

      • Air out your dry cleaned clothing before bringing them into your home.

      • Do not use air fresheners, scented fabric softeners or scented detergents.

      • Respect the scent-free policies at your work, school, in the hospital, etc.

Asthma and viral infections 

Viral infections such as a cold or the flu are a common cause of asthma symptoms, especially in kids.

Here are some ways to help prevent viral infections:

      • Get a flu shot every year.

      • Wash your hands regularly, especially after being in public.

      • Avoid touching your nose, eyes or mouth while in public.

      • If possible, avoid people who have colds or the flu.

      • Always keep your asthma under control so that if you do get a cold or the flu, it will be less likely to cause significant asthma symptoms.

      • Eat a healthy balanced diet and exercise regularly (every day if possible)

If you do get a viral infection, pay attention to your symptoms. If you start having symptoms, follow the directions in your asthma action plan. Your asthma action plan might direct you to take more of your asthma controller medication until your symptoms are under control again.

Click here to download or order your asthma action plan 

Asthma and medication triggers 

Make sure that your health care providers know all of the medications you take, even non-prescription and herbal medications.

Medications that can cause asthma symptoms in some people include:

      • Aspirin (anything with ASA in it) found in pain killers, cold remedies, arthritis medications

      • Beta Blockers (for high blood pressure, angina, glaucoma)

      • ACE Inhibitors (for high blood pressure, heart disease)

If you know you react to a medication, here are some ways to protect yourself:

      • If you do react to a medication, tell your doctor and pharmacist right away.

      • Absolutely avoid that medication.

      • Check with your doctor or pharmacist to find out if there are other medication options that are less likely to affect your asthma.

      • Use acetaminophen (eg., Tylenol) for pain relief.

      • Always check medication labels.

      • Get a MedicAlert bracelet, necklace or card to alert others if you have a dangerous allergy.

Asthma and exercise 


Did you know that many top athletes in Canada have asthma and successfully compete in their chosen sports? If you keep your asthma under control, you should be able to exercise just like everyone else.

Exercise can cause asthma symptoms but if you take these steps, asthma shouldn't usually stop you from exercising:

      • Keep your asthma under control.

      • Warm up before and cool down after the exercise.

      • If prescribed, take a reliever inhaler 5-10 minutes before exercising.

      • Cover your nose and mouth with a scarf when exercising outdoors in cold weather.

      • Move your exercise indoors if air pollution, pollen or cold winter air bother your asthma.

If symptoms such as coughing or wheezing occur when you exercise, your asthma is likely not under control. Speak with your health care provider to learn more about leading an active, healthy lifestyle with asthma.

Don't start exercising if you are experiencing asthma symptoms. If you begin to feel your asthma symptoms during exercise, stop immediately and take your reliever inhaler. Only start again if your symptoms are completely gone. Make sure you have your reliever inhaler with you at all times.

If asthma is limiting your ability to play sports or exercise, you may only need a simple change in your medication dose, or your doctor may prescribe an additional medication.


Asthma and sports 


Most people with asthma should be able to play most sports and do any exercise that other people do. One possible exception is scuba diving. Scuba diving is often not recommended for people with asthma and is even banned in some countries for those with asthma. If you have asthma and go diving, the airways in your lungs could close off if you have an attack when you're deep under water. Then if the pressure in your lungs is not able to equalize as you rise back up, this can be very dangerous. Ask your doctor for advice before trying scuba diving.

These sports tend to be harder on the lungs because they require continuous exertion:

      • soccer

      • hockey

      • basketball

      • lacrosse

      • triathlons

      • long-distance running

      • long-distance cycling

These sports have built-in breaks, so they may be easier to play (at least at a recreational level) if you have severe asthma or if your asthma is not fully controlled:

      • badminton

      • volleyball

      • tennis (especially doubles)

      • baseball

      • football

Winter sports such as hockey, cross-country skiing and figure skating are done in cold air, which can be a trigger.

With indoor sports such as badminton and volleyball, the air is warm and there is less exposure to outdoor pollens, moulds and air pollution.

Swimming is a great year-round exercise. Although pool chemicals may bother some people with asthma and pools may have some moulds, if you keep your asthma well controlled, these are much less likely to bother you.

Asthma and Hockey

In hockey, there are short breaks between whistles and when you're on the bench. However, when you're on the ice you may be continually exerting yourself while breathing in cold air. Make sure you keep your asthma well controlled, like the many NHL players who have asthma.