The exact cause of asthma is not completely known. It is believed to be partially inherited, but it also involves many other environmental, infectious, and chemical factors. After a person is exposed to a certain trigger, the body releases histamine and other agents that can cause inflammation in the airways. The body also releases other factors that can cause the muscles of the airways to tighten, or become smaller. There is also an increase in mucus production that may clog the airways.
Some persons have exercise-induced asthma, which is caused by varying degrees of exercise.
Symptoms can occur during, or shortly after, exercise. Each person has different triggers that cause the asthma to worsen. You should discuss this with your physician. This makes it initially difficult to breathe. A later response, which can happen four to eight hours after the initial exposure to the allergen, leads to further inflammation of the airways and obstruction of airflow.