Asthma Triggers

Triggers are things that make your child’s asthma worse. Your child has a set of asthma triggers that may be different from other children. It is important to know what your child’s asthma triggers are and try to remove or reduce them.

Common triggers include:

  • infections such as colds and flu
  • cigarette smoke and other irritants such as air pollution, cold air, and chemical fumes
  • allergens such as pet dander, dust mites, pollens, and moulds
  • certain medicines


    Some Common Asthma Triggers
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Infections such as colds and flu

Viral infections such as colds and flu are common asthma triggers. To help protect your child:

  • Keep your child away from people who have a cold or the flu.
  • Make sure your child and your family members wash their hands often.
  • Ask your doctor about getting the flu shot for your child early in the fall each year.
  • Remember to keep your child’s asthma under control all the time. This will help your child to have less asthma symptoms when your child does get a cold or the flu.


Irritants are things that can irritate your child’s airway and cause asthma symptoms. Even though sometimes it may be hard to stay away from irritants, there are ways to help your child avoid them.

Some examples of irritants are:

  • cigarette smoke
  • wood and oil smoke
  • air pollution
  • cold air
  • chemical fumes or strong odours

Cigarette smoke

Children’s asthma is frequently triggered by second-hand smoke. Here are some ways to protect your child from smoke:

  • If you smoke, try to quit.
  • Do not smoke in the house. Ask anyone who smokes to smoke outdoors.
  • Remember that cigarette smoke stays on clothes. If a person who has been near cigarette smoke is close to your child, this can make your child’s asthma worse.
  • Stay away from smoky areas. Help your child stay away from cigarette smoke when you are out.
  • Do not let anyone smoke in the car.

Wood and oil smoke

Smoke from a wood stove or a campfire may also be an irritant. Here are some ways to protect your child:

  • Keep your child away from the smoke of a fireplace, wood stove, or campfire.
  • Keep your child away from the smoke made by an oil heater.

Air pollution

Air pollution is highest during hot and humid days in the summer. Here are some ways to protect your child from air pollution:

  • Follow the air quality index on TV or online.
  • When air quality is poor outside, try to let your child stay indoors where air conditioning is available. This might be an air-conditioned home, a shopping mall, or an office building.
  • Keep the windows closed at home and in the car when the air quality is poor. Turn on air conditioning if possible.

Cold air

Your child’s asthma may get worse if there is a sudden change in temperature. Here are some ways to prevent cold air from triggering an asthma episode:

  • Before your child goes out in cold weather, make sure your child wears a scarf that covers the nose and mouth. This can help to warm and humidify the air that your child breathes in.
  • Let your child exercise indoors on cold days.
  • You may need to ask your child’s teacher to let your child stay indoors during recess.

Chemical fumes and strong odours

Some strong scents and chemical fumes can irritate your child’s airway. Some examples include:

  • cleaning products
  • paints and paint strippers
  • perfumes
  • bleach
  • air fresheners
  • pesticides

Here are some ways to protect your child from these irritants:

  • Keep your child away from chemical fumes and strong odours.
  • Try to keep the windows open and air out after you paint a room. Let your child go into the room after the scent is gone.


Allergens are things that your child is allergic to. Not every child with asthma has allergies. But if your child has allergies, it is important to control or stay away from the allergens that bother her.

Allergens can make a child’s asthma worse when they are breathed in. Allergens make the airways in the lungs become inflamed and narrow. This makes it hard for air to pass through. It can cause coughing, wheezing, feeling short of breath, and other asthma symptoms.

Some examples of allergens include:

  • pet dander
  • dust mites
  • pollens
  • moulds

Pet dander

If your child is allergic to pets, the best way to avoid asthma episodes is to find another home for your pets. It is very important to clean your house thoroughly after the pet is removed, because traces of the animal can stay in living areas for a long time. You may need to clean furniture, carpets, children’s stuffed toys, and the heating and cooling system.

Dust mites

Dust mites are very tiny bugs that feed off shed human skin. Children who have dust allergies are actually allergic to the droppings of dust mites. Dust mites live mostly in warm and moist places with lots of shed human skin, such as mattresses, pillows, bedding, carpets, rugs, and upholstered furniture. In order to control your child’s allergy, you must remove all the droppings and kill the dust mites.

Some helpful actions are:

  • Wash all your linens in very hot water every week.
  • Cover your child’s mattress, box spring, and pillows with special allergen-proof covers or impermeable covers that completely enclose the mattress.
  • Remove carpets, rugs, and heavy curtains from your child’s bedroom. Ideally, remove them from the rest of the house if possible.
  • Remove stuffed animals or dolls from your child’s bedroom or store them in the closet. Reducing clutter in the bedroom will mean less dust can collect.
  • Vacuum the carpet and dust every week.
  • Keep the humidity level in the house below 50%. You can use a dehumidifier in damp areas. Dust mites do not survive well in dry environment.


Pollens are from trees, grasses, and weeds. They can travel for miles by wind and are most problematic during the spring and warm-weather months.

If your child is allergic to pollens, there are a few things you can do to help your child avoid them:

  • Close the windows at home and in the car as much as you can on days when the pollen count is high. Use an air conditioner if needed and change the filter regularly.
  • Watch for the pollen count and decide if your child should stay home on days when the count is high. You can check pollen reports on TV or online.
  • If your child does go out when the pollen is high, have her shower and change clothes when she comes home.
  • Dry your child’s laundry using a clothes dryer instead of hanging clothes and sheets outside.


Moulds grow all year round in areas that are damp, such as basements and bathrooms. They can travel in the air to anywhere in the home.

Here are some ways you can keep your house free of moulds:

  • Use soap or detergent and water to clean up small areas of mould in your home. For larger areas, you may need a substance that is specifically for killing mould (a fungicide).
  • Use a dehumidifier in damp areas of your home, such as the basement. Keep the humidity in your home to less than 50%.
  • Ventilate your home well; moulds do not live well in airy areas.
  • Open the window or use a bathroom fan after showers.
  • Fix water leaks in the roof or plumbing immediately.


Food allergies do not usually cause asthma symptoms, but children with food allergies are more likely to develop asthma. In addition, children with food allergies may be more likely to have severe asthma, so it is very important to keep asthma under good control if your child has food allergies. The most common food items that account for food allergies in children are milk, eggs, peanuts, nuts, wheat, soy, shellfish, and fish.

If you suspect that your child is allergic to certain food, consult an allergist.


Certain medicines, ASA (acetylsalicylic acid or Aspirin) and ibuprofen, can cause asthma symptoms in some children with asthma.

If your child is sensitive to these medicines, tell your pharmacist. Make sure there are no words like ibuprofen, Aspirin, ASA, or acetylsalicylic acid​ on the labels of the medicines that you give your child.

Sharon Dell, BEng, MD, FRCPC

Bonnie Fleming-Carroll, MN, ACNP, CAE

Jennifer Leaist, RN, BScN

Rishita Peterson, RN, BScN, MN

Gurjit Sangha, RN, MN

James Tjon, BScPhm, PharmD, RPh