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Asthma FAQs (cont.)

What Causes Asthma?

While there is no known specific cause of asthma, what all people with asthma have in common is chronic airway inflammation. Their airways are highly sensitive to various triggers. When their airways come into contact with a trigger, the airways become inflamed (they fill with mucus, swell, and narrow). Then muscles within the airways contract, causing even further narrowing of the airways. This makes breathing difficult and results in an asthma attack.

Triggers are different for different individuals. Common ones include the following:

  • Exposure to tobacco smoke
  • Breathing polluted air
  • Inhaling irritants such as perfume and cleaning products
  • Allergens such as molds, dust, and animal dander
  • Exposure to cold, dry weather
  • Stress
  • Exercise or physical exertion
  • Medications including aspirin and nonsteroidal antiinflammatory drugs, such as ibuprofen
  • An upper respiratory infection such as a cold, flu, or bronchitis
  • Sulfites (additives to some foods and wines)

Changes in weather can also trigger asthma attacks because of the irritants and allergens stirred up by wind and rain.

Asthma is on the rise in the United States and other developed countries. While the reasons are not clear, the following factors may contribute to the rise:

  • Spending more time indoors where exposure to indoor allergens such as dust and mold and some chemicals from building materials is greater
  • Living in cleaner conditions than people did in the past, which makes our immune systems more sensitive (reactive) to triggers
  • Exposure to increased air pollution
  • Increased physical inactivity (lack of exercise)

Who Gets Asthma?

Asthma affects millions of people worldwide. The number of people affected is eight to 10 times higher in industrialized countries than in developing ones.

Children age 10 and younger account for half of asthma cases. In most children, asthma develops before they are 5 years of age, and in more than half, asthma develops before they are 3 years of age.

More than twice as many boys than girls have asthma, although boys are more likely to experience a decrease in symptoms as they reach adolescence. In adult-onset asthma, the number is reversed. Twice as many women than men visit the emergency department and are admitted to the hospital with asthma.

Asthma affects all races worldwide but is more common in blacks and Hispanics, but this may be due to socioeconomic conditions rather than genetics.

Occupational asthma (asthma triggered at work by exposure to irritants present at the workplace) is most common in those who work with animals or animal-derived products and in industries such as plastics, rubber, chemical, textile, electronics, painting, printing, metalworking, baking, and gardening.

Risk factors for asthma include the following:

  • Smoking or living with a smoker is a major risk factor. A significant percentage of children who have asthma have at least one parent who smokes.
  • A family history of asthma: If one parent has asthma, a person has a 25% chance of developing it. If both parents have it, a person has a 50% chance of manifesting asthma.
  • Having allergies, including hay fever and eczema: It is not known why some people have allergies and some don't, but allergies can be inherited (although people don't necessarily develop the same allergies as their parents have).
  • Having allergies or severe viral infections before the age of 3
  • Living in the inner city, especially in a low-income group
  • Being exposed to mice and cockroach waste products
  • Frequently being exposed to triggers
Medically Reviewed by a Doctor on 4/4/2016

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