The number of people diagnosed with asthma is growing each year, but no one really knows why some people are affected while others are not. There are a number of asthma risk factors that are thought to increase a person’s chance of developing asthma.

Asthma risk factors include:

Family History

Genetics play a role in determining how likely you are to have asthma. If one of your parents has asthma, then you have a greater risk of developing it.

Gender and Age

These two risk factors go hand-in-hand. Asthma most often begins in childhood and is more common in children than adults. However, some people don’t develop asthma until later in life (adult-onset asthma). During childhood, boys are more likely to have asthma than girls. During early adulthood, the risk for men and women is this same.

Allergies

Asthma and allergies are closely linked. Sensitivity to allergens—such as dust, pet dander, mold, and toxic chemicals – is often an accurate predictor of your potential to develop asthma, and those allergens can trigger asthma attacks after you develop asthma.

Smoking

Cigarette smoke irritates the airways, and research has shown smokers to have a greater risk of asthma. Those whose mother smoked while pregnant or who were exposed to second-hand smoke (especially early in life) are also more likely to have asthma.

Air Pollution

Ozone, the main component of smog, is created when chemicals from industrial factories mix with sunlight. If you grew up or live in an urban area and are exposed to smog, you are more likely to suffer from asthma. Studies have shown that children who live in high-smog areas are at a much greater risk—especially if they play outdoor sports—than those who live in low-ozone cities.

Obesity

Research has show that children and adults who are overweight or obese are at a greater risk of asthma. The reasons asthma and obesity are related are still unclear. However, some experts point to low-grade inflammation that occurs throughout the body as a result of obesity. Evidence has proven that losing weight relieves asthma symptoms.

Viral Respiratory Infections

Respiratory conditions during infancy and childhood can cause wheezing. Some children who experience viral respiratory infections go on to have chronic asthma. The role of the infection is unclear, but it is possible there is some connection to asthma.