We do not know exactly what causes asthma.
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 as asthma attack.
In asthma the "invaders" are the triggers listed below. Triggers vary by the individual.
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 - What medical professionals call gastroesophageal reflux disease, or GERD
Sulfites - An additive to some foods and wine
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 - The single biggest risk factor
Eczema - Another type of allergy affecting the skin
Genetic predisposition - A parent, brother, or sister also has asthma