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Asthma is a chronic disease involving the inflammation, increased sensitivity (hyperresponsiveness), and narrowing of the airways leading to episodes of asthma attacks characterized wheezing, shortness of breath, chest tightness, and coughing. It affects 10% of Canadians and its prevalence is increasing, having doubled in the past century. It is the most common reason for hospital visits by children.

Asthma attacks can be triggered by environmental factors including allergies, irritants, respiratory illnesses, exercise, sudden changes in weather, strong emotions, and reflux. Genetics also play a role in asthma. A child is more likely to have asthma if either parent or both parents are asthma.

In non-asthmatic individuals, air is able to freely enter and exit your lungs through your airways without any obstruction. Asthmatic individuals have increased inflammation (swelling) and hyperresponsiveness of the airway. Airway hyperresponsiveness is the increased sensitivity of the airway to triggers leading to increased inflammation, mucus production, and tightening of the muscles around your airway resulting in further narrowing of the airway and difficulty breathing (asthma attack).

Allergic asthma is the most common form of asthma, accounting for 60% of asthma cases. In allergic asthma cases, allergens cause the release of inflammatory mediators such as histamines by mast cells in the airway, which lead to further inflammation, mucus production, and constriction of the muscles surrounding the airway. Allergens also activate a special type of immune cell called a TH2 cell which release another inflammatory mediator called IL-5 that also contributes to inflammation. Allergens therefore cause narrowing of the airway resulting in an asthma attack.

What is Asthma?

Cause of Asthma

Symptoms of Asthma


Reduces inflammation and hyperresonsiveness of airways to reduce the frequency of asthma attacks.


Rapidly open up airways during an asthma attack by relaxing the muscles surrounding your airway.


Babies may use inhaled corticosteroids in the form of nebulizers (creates mist for babies to breath through using a small face mask) or through an inhaler with a spacer and small face mask.

For information on how to use inhalers, including the use of inhaler for infants babies, please visit out Instructional Videos page.



Blausen.com staff (2014). "Medical gallery of Blausen Medical 2014". WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436.