Asthma can happen to anyone, 
but there are some factors that make your risk of developing asthma much more likely:
Gender
In childhood, asthma is more frequently developed by boys than by girls. Some studies show this is linked to males having smaller airways in childhood than females, but this hasn’t been proven. The reverse is true in adulthood – women are more likely than men to have asthma.
Family History
You can inherit a predisposition to asthma from your parents. According to the Asthma and Allergy Foundation of America, if one parent has asthma, chances are one in three that their children will have asthma. If both parents have asthma, the chance their children will have asthma is seven in 10.
Allergic Hypersensitivity
Allergic hypersensitivity can include eczema, allergic rhinitis, allergic conjunctivitis and asthma. As they are all related conditions, odds of having more than one are greater – Meaning if you have eczema, you have a higher chance of developing asthma.
Allergies
Allergies and asthma often go hand in hand, as both are inflammatory conditions. Allergies are also a trigger in asthma attacks for many people with asthma.
Environmental Factors
Exposure to indoor pollution such as smoke, mold and fumes, and outdoor pollution such as ozone and air pollution can cause allergic reactions and asthma in some people.
Cigarette Smoking
Cigarette smoke, firsthand or secondhand, can lead to asthma in adults and children. Smoking during pregnancy can cause lower lung function in children and lead to premature birth, which has been shown to be a factor in children developing asthma.
Obesity
Asthma is more common in overweight adults and children. Studies have also shown that overweight asthmatics are more likely to have uncontrolled asthma.
Some of these risk factors cannot be avoided or controlled, but changing your lifestyle to lessen the impact of factors that are in your control can lower your risk for developing asthma.