The cause of
asthma isn't known. Health experts believe that
inherited, environmental, and
immune system factors combine to cause
inflammation of the airways. This can lead to asthma and
Asthma may run in families (be inherited). If
this is the case in your family, you may be more likely than other people to
get long-lasting (chronic) inflammation in the airways.
In some people,
an allergic reaction causes asthma symptoms. An allergen makes the immune system cells release chemicals that cause
Studies show that exposure to
allergens such as
dust mites, cockroaches, and
animal dander may influence asthma's
development.1 Asthma is much more common in people
with allergies, although not all those who have allergies get asthma. And not
all people with asthma have allergies.
Environmental factors and
today's germ-conscious lifestyle may play a role in the development of asthma.
Some experts believe that there are more cases of asthma because of pollution
and less exposure to certain types of bacteria or infections.2 As a result, children's immune systems may develop in a way
that makes it more likely they will also get allergies and asthma.
Asthma in adults also can be related to work. This is called occupational asthma.