Reviewed by David Tinkelman, MD

Although the actual cause of asthma is not known, many studies have shown that several factors can lead to the development of asthma. These factors include a person's genetics, development and growth of the lungs and immune system, various infections and exposures in the environment.


Link to Genetics
It is widely accepted that asthma is a disease that can be inherited. However, the gene or genes that are involved are not clearly identified. It is believed that the genes linked to asthma involve the lungs and the immune system. It is well known that the atopic diseases - atopic dermatitis, allergic rhinitis and asthma - are commonly found in one form or another within families.

Childhood Development
The early months and years of a child's life are critical times during which a baby can develop or become susceptible to developing asthma. The abnormal development and growth of the lungs can increase a person's risk for developing asthma. Premature babies born with lungs not fully developed are more susceptible to colds and other respiratory infections. In some cases, an infection can cause inflammation and injure lung tissue. If the baby is exposed to secondhand smoke at this time, more damage to the lungs may occur and change how the lungs function.

The Immune System's Role
Many studies have shown that children and adults with asthma have an immune system that responds differently from those who do not have asthma. Many of these people with asthma are allergic and will react to things that do not cause problems in others. Their immune system overreacts when they come in contact with everyday substances such as pollens, mold, or cat dander. In some cases, the immune system may overreact to other substances, such as a virus or bacteria, and increase the risk of asthma.

Environmental Exposures
There are many non-allergic or non-immunologic exposures in the environment that can increase the chance of developing asthma. Exposure to irritants on a long-term basis, such as secondhand smoke in the home, is a major risk factor for developing asthma. Other exposures like this are indoor chemicals and air pollution. Some studies suggest that certain infections or allergy exposure during the first years of life may also affect the development of asthma.

More Research
More research is being done to better understand the role of genetics, infections, exposures, and the immune system in the development of asthma and other allergic disorders. This information may help to prevent the development of these problems in the future.

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