About one third of all persons with asthma share the problem with another member of their immediate family. Genetic factors appear to play a more important role than common environmental factors in such families, and the condition may be more likely to be passed to children from the mother than from the father. One study also reported that the risk of having an asthmatic child was six times higher if both parents had a history of asthma than if just one had the disease. One study found that specific genetic regions increase the risks for asthma in different ethnic populations, including African Americans, Hispanics, and Caucasians. It occurs most often in children and young adults with asthma and is distinct from ordinary allergic asthma.
People can have one or both types.
Although exercise-induced asthma has the same symptoms as allergic asthma, it is not dangerous and does not require hospitalization. EIA occurs most often during intense exercise in cold dry air. The organisms Chlamydia pneumoniae , Mycoplasma pneumoniae , adenovirus, and respiratory syncytial virus are major causes of respiratory infections and are becoming important suspects in many cases of severe adult-onset asthma. Recently, a study reported that antibiotic treatment in childhood was highly associated with both later asthma and hay fever. Such a finding may support the role of infections as a cause of asthma or it may mean that antibiotics themselves directly affect the immune system.