However, much is known about the risk factors for the disease—some factors you can change and others you cannot. For example, asthma is more common in boys than girls and in children in urban areas than other parts of the country; plus, it is more likely to be diagnosed in people who are obese than in those who are slender.
About 9% of the U.S. population under age 18 has asthma. Studies involving twins have found that a child’s chance of developing asthma is anywhere from 50% to 80% dependent on genes, but the environment in which a child lives and grows is also very important. Exposure to dust, pet dander, pollution, exhaust, and secondhand smoke can all increase a child’s risk for asthma. These allergens and irritants can also trigger the sudden exacerbation of asthma symptoms known as an asthma attack.
To learn more about the causes and risk factors of asthma in children, check out the following information from our A–Z Health Library. The causes and risk factors for asthma in adults are similar to those in children.
Many factors may increase the risk of a child developing asthma. Some of these are not within your control; others you can control.
Asthma risk factors that you cannot control
- Gender. Among children, boys have asthma more often than girls.
- Race. Asthma is more common in black children than in white children.5
- Inherited tendency (genetic predisposition) to overreaction of the bronchial tubes. Children who inherit a tendency of the
bronchial tubes
(which carry air to the lungs) to overreact often develop
asthma. - A history of allergies. Children with an allergy are more likely than other children to develop asthma. Most children with asthma have allergic rhinitis, atopic dermatitis, or both. Studies show that 40% to 50% of children with atopic dermatitis develop asthma. Having atopic dermatitis as a child may also increase the risk of a person having more severe and persistent asthma as an adult.6
- A family history of allergies and asthma. Children who have an allergy and asthma usually have a family history of allergies or asthma.
- Respiratory syncytial virus (RSV) and wheezing at a young age. Early infection with respiratory syncytial virus (RSV) that causes a lower respiratory infection is a risk factor for wheezing.7 Young children who wheeze have a greater risk of developing asthma than children who do not wheeze.
Asthma risk factors that you can control
You may be able to change some factors to reduce your child's risk of developing asthma or of making the condition worse.
- Cigarette smoking. Children who smoke are more likely to develop asthma when they become teenagers. A large study found that children who smoked at least 300 cigarettes in a year were almost 4 times more likely to get asthma.8
- Cigarette smoking during pregnancy. Women who smoke during pregnancy increase the risk of wheezing (a symptom of asthma) in their babies. Babies whose mothers smoked during pregnancy also have worse lung function than babies whose mothers did not smoke.9
- Exposure to secondhand cigarette smoke. Children who are exposed to secondhand cigarette smoke are at increased risk for developing asthma.9 If children already have the disease, exposure to secondhand smoke increases the severity of their symptoms.
- Obesity. Studies have found a link between obesity in children and a higher-than-average asthma prevalence. But the reason for the link is unclear. Experts don't know whether one condition contributes to the other or whether some unknown mechanism contributes to both.5 Also, symptoms caused by obesity are sometimes thought to be asthma symptoms.
- Dust mites. Exposure to dust mites may increase your child's risk for developing asthma.9
- Cockroaches. In one study, children who had a high level of cockroach droppings in their home were 4 times more likely to have a new diagnosis of asthma than children whose homes have a low level.9
No one is sure if breast-feeding affects a child's risk of getting asthma. Some studies show that breast-feeding protects a child from getting asthma.10, 11 Other studies show that breast-feeding, especially when mothers with asthma breast-feed, may actually increase a child's risk of getting asthma.12 Two large studies found that breast-feeding had no effect on the development of asthma.13, 14 Mothers are still encouraged to breast-feed their children for all the other proven health benefits that come from breast-feeding.
Experts are also not sure about the effect that pets in the home have on getting asthma. Some research shows that having cats or dogs in the home increases an adult's risk of getting asthma.15 But other research has seemed to show that being around pets early in life might protect a child against getting asthma.16 If your child already has asthma and allergies to pets, having a pet in the home may make his or her asthma worse.
Risk factors that may make asthma worse and may lead to asthma attacks
Your child may be at increased risk for severe asthma attacks if he or she:
- Is an infant.
- Has a history of severe symptoms, such as asthma attacks that get worse quickly and frequent nighttime symptoms.
- Has had to go to the hospital or emergency room in the past because of an asthma attack.
- Has difficulty taking medicines or often has to use short-acting beta2-agonists.
- Has frequent changes in peak expiratory flow.
- Has symptoms that last for a long time.
- Does not use oral corticosteroids quickly enough during an attack.
- Does not have good support from families and friends.
Triggers that may make asthma worse and may lead to asthma attacks in your child include:
- Infections, such as severe upper respiratory infections (URI), sinusitis, and influenza (flu).17
- Allergens, such as dust mites, mold, or pet dander.9
Last Updated: March 20, 2009 
