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Asthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Asthma is clinically classifiedaccording to the frequency of symptoms. Asthma may also be classified as atopic (extrinsic) or non-atopic (intrinsic).
Causes
Asthma is caused by environmental and genetic factors. These factorsinfluence how severe asthma is and how well it responds to medication. The interaction is complex and not fully understood. In children between the ages of 3–14, a positive skin test for allergies and anincrease in immunoglobulin E increases the chance of having asthma. Strict reduction of dust mite allergens, for example, reduces the risk of allergic sensitization to dust mites, and modestlyreduces the risk of developing asthma up until the age of 8 years old. However, studies also showed that the effects of exposure to cat and dog allergens worked in the converse fashion; exposure during thefirst year of life was found to reduce the risk of allergic sensitization and of developing asthma later in life. Several factors associated with obesity may play a role in the pathogenesis of asthma;including decreased respiratory function due to a buildup of adipose tissue and the fact that adipose tissue leads to a pro-inflammatory state, which has been associated with non-eosinophilic asthma.Maternal tobacco smoking during pregnancy and after delivery is associated with a greater risk of asthma-like symptoms, wheezing, and respiratory infections during childhood. Low air quality, fromtraffic pollution or high ozone levels, has been repeatedly associated with increased asthma morbidity and has a suggested association with asthma development that needs further research.
SymptomsCommon symptoms of asthma include wheezing, shortness of breath, chest tightness and coughing, and use of accessory muscle. Symptoms are often worse at night or in the early morning, or in response to...