Asthma - Causes

In most cases, asthma is caused by inhaling an allergen. That allergen then sets off a series of reactions in the body that cause inflammation of bronchi and bronchioles. The most common inhaled allergens that lead to asthma attacks are:

  • Animal dander (dry skin that is shed)
  • Chemicals, fumes, or tiny particles that occur in the air in workplaces
  • Fungi (molds) that grow indoors
  • Mites found in house dust
  • Pollen

Tobacco smoke is another cause of asthma attacks. The smoke irritates bronchi and bronchioles, setting off an asthma reaction. The same effect is caused whether an individual himself is smoking or is inhaling smoke second-hand (from someone else). Air pollutants can have a similar effect.

Three other factors can produce asthma attacks. They are:

  • Exercise (exercise-related asthma)
  • Inhaling cold air (cold-induced asthma)
  • Stress or anxiety

Other factors that can cause an asthma attack or make it worse are rhinitis (pronounced ri-NIE-tuss; inflammation of the nose), sinusitis (pronounced sie-nuh-SIE-tis; inflammation of the sinuses), acid reflux (known as acid stomach), and viral infections of the respiratory (breathing) system.

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