Many factors may increase your risk of developing asthma. Some of these are not within your control; others you can control. The major risk factors for developing asthma as an adult are ongoing (chronic) wheezing when you were a child and cigarette smoking.⁵

Asthma risk factors that you cannot control

The following risk factors are not within your control:

• Gender and age. Women and men seem to have the same risk of developing asthma until they reach their 40s. After 40, women have a higher risk for asthma.
• A family history of allergies and asthma. People who have an allergy and asthma usually have a family history of allergies or asthma.
• Inherited tendency (genetic predisposition) to overreaction of the bronchial tubes. People who inherit a tendency of the bronchial tubes (which carry air to the lungs) to overreact often develop asthma.
• A history of allergy. If you have an allergy, you are more likely than others to develop asthma. Most children and many adults with asthma have atopic dermatitis, allergic rhinitis, or both. Studies indicate that 40% to 50% of children with atopic dermatitis develop asthma. Having atopic dermatitis as a child may also increase your risk of having more severe and persistent asthma as an adult than someone who did not have atopic dermatitis.⁶
• Rhinitis. Adults who have inflamed nasal passages (rhinitis) have a higher-than-average risk of developing asthma.

Asthma risk factors that you can control

You may be able to change some factors to reduce your or your teen's risk of developing asthma. These include:

• Cigarette smoking. People who smoke are more likely to get asthma. If you already have asthma and you smoke, it may make your symptoms such as wheezing worse.
• Cigarette smoking during pregnancy. Women who smoke during pregnancy increase the risk of wheezing in their babies. Babies whose mothers smoked during pregnancy also have worse lung function than those whose mothers did not smoke.
• Workplace exposure to irritants. Occupational asthma may develop after exposure to a specific inhaled irritant or allergen in the workplace. Such substances also can make symptoms worse in people with existing asthma.
• Dust mites. Exposure to dust mites is a risk factor in the development of asthma.⁷
• Cockroaches. In one study, children who had high levels of cockroach droppings in their homes were 4 times more likely to have a new diagnosis of asthma than children whose homes had low levels.⁷
• Obesity. Studies have found that obese children may be more likely to have asthma. But the reason for this is unclear. Experts don't know whether one condition contributes to the other or whether some unknown mechanism contributes to both.⁸ Some people who are obese and who lose weight may have fewer asthma symptoms. And sometimes symptoms caused by obesity are thought to be asthma symptoms.