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Asthma is a very common chronic (long-term) lung disease that can make it hard to breathe. About 2.4 million Canadians aged 12 and older have asthma1. Over 1.9 million Ontarians have asthma2, including one out of every five children3If you manage your asthma well, it doesn't have to limit what you can do.  Unfortunately asthma can sometimes be fatal. In 2009, 228 Canadians died from asthma (91 in Ontario)4. Although there is no cure for asthma, it can be managed. With proper management, people with asthma can lead normal, active lives.

If you have asthma, your airways (breathing passages) are extra sensitive. When you are exposed to one of your asthma "triggers", these extra-sensitive airways can:

  1. Become red and swollen: Your airways get inflamed (swollen) inside and can fill up with mucus. This swelling and mucus make your airways narrower, so it's harder for the air to pass through.
  2. Become "twitchy" and go into spasm: The tiny bands of muscles around your airways can tighten up. This makes your airways narrower, leaving less room for the air to pass through.

The more red and swollen your airways are, the more they can spasm.


Airway of a person without asthma or with their asthma under control Airway of a person with uncontrolled asthma - swelling (inflammation) Airway of a person with uncontrolled asthma - tightened muscles (bronchospasm)






Normal Airway






Airway with Uncontrolled Asthma


Asthma Types


There are many terms that health care providers and the general public use to describe the different asthma types, such as:

        • childhood asthma
        • allergic asthma
        • adult onset asthma
        • occupational asthma
        • bronchial asthma
        • acute asthma
        • chronic asthma
        • coughing asthma or cough variant asthma
        • exercise-induced asthma or sports-induced asthma
        • viral asthma or viral-induced asthma
        • acid reflux asthma
        • aspirin-induced asthma

All of these different terms are describing variations of a similar thing. Your lungs are reacting to something that leads to swelling, extra mucus, and airway spasm (tightening of the muscles that surround your airways), which lead to the common symptoms of coughing, shortness of breath, chest tightness or wheezing.

These different terms are related to when you get asthma, what causes your symptoms, or what your main symptom is. Although these terms have some meaning, the same basic strategies apply to everyone with asthma:

      1. Avoid the things that make your asthma worse. These are called "asthma triggers".
      2. Take proper medications to keep away the inflammation, mucus and tightening of the airways, so that you can breathe easy.

What causes asthma? Who is at risk of getting it? 


It is important to know the difference between the factors that cause asthma to develop in a person, and the factors that can trigger symptoms in someone who already has asthma. There is quite a bit known about asthma triggers, but the causes of asthma are not too well known. There is a need for more research to determine the causes of asthma so that in the future we may be able to prevent it.

Although some of the evidence is not conclusive, here are some factors that may make it more likely that a person will get asthma:

Genetics: One thing we know for sure is that asthma and allergies can be passed on in the family genes. If people in your family have allergic diseases like asthma, hay fever (allergic rhinitis), or eczema, there is a higher chance you will have asthma. This does not mean that if you have asthma or allergies in the family that you will get asthma for sure. It just means that you have a higher chance of getting asthma. Also, if there are no allergies or asthma in your family, you can still get asthma.

Tobacco smoke: Children whose mothers smoked while pregnant or who grow up in a smoky home are more likely to get asthma.

Indoor allergens: Exposure to dust mites, pet allergens, moulds, and cockroach allergens have all been suggested as possible causes of asthma. However, there is still a need for more research to confirm this.

Outdoor air pollution: Some research shows that people who live near major highways and other polluted places are more likely to get asthma.

Infections: Certain viral infections during infancy (eg. RSV) have been associated with later developing asthma or asthma-like symptoms. However, there is still a need for more research to confirm this.

Gender: Boys are more likely to get asthma than girls. However during adolescence this slowly changes and by adulthood, more women have asthma than men.

Obesity: Research has suggested that obesity may be a risk factor for developing asthma. More research is needed.

Occupational asthma: People who work in certain types of jobs may have a higher chance of developing asthma from an exposure at work. This is called occupational asthma.


1   Statistics Canada. Table 105-0501.

2   OASIS Website:

3   OASIS Website:

4   Statistics Canada. Catalogue no. 84F0209X - Mortality, Summary List of Causes 2009 Times