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Understanding Asthma -- the Basics

What Causes Asthma?

Asthma is usually not a problem with breathing in, but with breathing out. Asthma is a chronic illness with three main features:

  • Inflammation of the airways of the lungs
  • Constriction (bronchospasm or narrowing) of the airways (bronchioles) due to contraction of the muscles that surround the airways that is reversible
  • Extreme sensitivity of the airways to certain asthma triggers which cause them to quickly constrict, slowly become swollen, and secrete more mucus


Asthma and allergies are much more common in people with a family history of asthma or allergies. The factors which worsen asthma vary from individual to individual. Each person with asthma should seek to determine exactly which factors cause their asthma to worsen. Common asthma triggers include:

  • Allergies, such as allergies to house dust mites, cockroaches, cats, dogs, molds, mice, and grass, weed, and tree pollens
  • Infections, colds, influenza, and other respiratory viruses
  • Irritants, such as strong odors from perfumes or cleaning solutions, air pollution, and especially smoke from tobacco, incense, candles, or fires
  • Exercise, especially in dry or cold environments
  • Cold or dry weather and changes in temperature and/or humidity, such as with thunderstorms
  • Strong emotions, such as anxiety, laughter, or crying (which can cause heavy breathing)
  • Reflux of acid from the stomach (GERD)
  • Pain medications, such as aspirin or NSAIDs (10% of those with asthma are aspirin and NSAID sensitive)

WebMD Medical Reference

Reviewed by Luqman Seidu, MD on February 28, 2015
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