Asthma Causes

The exact cause of asthma is not known.

• What all people with asthma have in common is chronic airway inflammation and excessive airway sensitivity to various triggers.



• Research has focused on why some people develop asthma while others do not.



• Some people are born with the tendency to have asthma, while others are not. Scientists are trying to find the genes that cause this tendency.



• The environment you live in and the way you live partly determine whether you have asthma attacks.

An asthma attack is a reaction to a trigger. It is similar in many ways to an allergic reaction.

• An allergic reaction is a response by the body's immune system to an "invader."



• When the cells of the immune system sense an invader, they set off a series of reactions that help fight off the invader.



• It is this series of reactions that causes the production of mucus and bronchospasms. These responses cause the symptoms of an asthma attack.



• In asthma, the "invaders" are the triggers listed below. Triggers vary among individuals.



• Because asthma is a type of allergic reaction, it is sometimes called reactive airway disease.

Each person with asthma has his or her own unique set of triggers. Most triggers cause attacks in some people with asthma and not in others. Common triggers of asthma attacks are the following:

• exposure to tobacco or wood smoke,



• breathing polluted air,



• inhaling other respiratory irritants such as perfumes or cleaning products,



• exposure to airway irritants at the workplace,



• breathing in allergy-causing substances (allergens) such as molds, dust, or animal dander,



• an upper respiratory infection, such as a cold, flu, sinusitis, or bronchitis,



• exposure to cold, dry weather,



• emotional excitement or stress,



• physical exertion or exercise,



• reflux of stomach acid known as gastroesophageal reflux disease, or GERD,



• sulfites, an additive to some foods and wine, and



• menstruation: In some, not all, women, asthma symptoms are closely tied to the menstrual cycle.

Risk factors for developing asthma:

• hay fever (allergic rhinitis) and other allergies -- this is the single biggest risk factor;



• eczema: another type of allergy affecting the skin; and



• genetic predisposition: a parent, brother, or sister also has asthma.

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