Asthma is defined by the Canadian Respiratory Society as "a disorder of the airways characterized by paroxysmal or persistent symptoms (dyspnea, chest tightness, wheeze and cough), with variable airflow limitation and airway hyper-responsiveness to a variety of stimuli."5

Clinical Picture

A precise diagnosis of a given respiratory complaint is complicated by the fact that there may be multiple causes from both indoor and outdoor sources, symptoms are often non-specific and may be atypical in children. Symptoms may also be non-distinct when there is exposure to low levels of pollutants, or they may mimic those related to allergic responses or respiratory infections.4

Children can present with a range of respiratory and related symptoms including:
  • sneezing
  • wheezing
  • sore throat
  • coughing
  • shortness of breath
  • chest tightness
  • hyper-responsive bronchi
  • irritated eyes, nose

The physician will have to carefully consider the variety of possible environmental exposures that might be influencing the child’s respiratory health when deciding on the differential diagnosis.


  • Asthma is the most common chronic childhood illness and has substantially increased in prevalence over the last two decades. In Canada, research indicates that there has been a fourfold increase in asthma prevalence in children under age 15 in the last 15 years.6
  • The exact etiology and pathogenesis of asthma is poorly understood, although it is likely a result of both genetic (i.e., inherited differences) and environmental influences. It is believed that asthma may be initiated by exposure to indoor air allergens, including those from house dust mites, cats, cockroaches and moulds. Children’s exposure to indoor allergens and pollutants has increased as houses and buildings have become more airtight with reduced air exchange and ventilation.
  • Indoor and outdoor air quality definitely contributes substantially to the burden of illness from asthma. Exposure to pollutants in air appears to trigger asthmatic attacks and/or worsen existing symptoms.

The latest Canadian Asthma Consensus Report (1999) includes a summary of recommendations regarding the diagnosis, control and treatment of asthma. Published in the Canadian Medical Association Journal (Boulet L-P et al. CMAJ 1999;161(11Suppl):S1-S62

The Canadian Pediatric Society Web site links to guidelines for emergency management of pediatric asthma.

A Health Canada study reports on Childhood Asthma in Sentinel Health Units: Findings of the Student Lung Health Survey 1995-1996.

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