The term pathophysiology of asthma means the abnormal body functioning that causes asthma. The airways themselves are not abnormal in someone with asthma, though asthma may lead to some permanent changes in the airway known as remodeling of the airway. The pathophysiology of asthma begins with an abnormal reaction of the immune system and this reaction’s effects on the airways.

When the immune system is hypersensitive to a substance or trigger, the immune system reacts as if the substance is harmful. The substance that triggers a response from the immune system is called an allergen. The allergen is a harmless substance like dust or pollen that the immune system mistakes for a harmful substance such as a dangerous virus.

Many cells are involved in this immune system response that causes asthma. Eosinphils, mast cells, epithelial cells, macrophages and activated T lymphocytes are some of the types of cells that are involved in the reaction. Mast cells, macrophages, and other cells release inflammatory mediators. Inflammatory mediators provoke other inflammatory cells to collect in the airways. The epithelial cells become inflamed and may sustain permanent damage in the process known as the remodeling of the airway.

The smooth muscle around the airways constricts. The constriction of the muscles and the inflammation of the lining of the airways narrow the diameter of the airways which makes it more difficult for someone with asthma to breathe. In addition to these asthma symptoms, mucous production increases in response to the allergen. The increased mucous further lessens the room for air to pass through the airways. The airways may become blocked by a mucous plug.

The constriction, inflammation, and swelling of the airways cause the airways to be sensitive to any allergens. These physiological changes also cause the signs of asthma. Wheezing, tightness of the chest, chest pain, and difficulty catching one’s breath are signs of asthma that are directly related to the physiological changes that take place in the airways. Asthma medications work to reduce inflammation and stop the immune system reaction that is causing the physiological changes.

Once there have been physiological changes in a response to an allergic reaction, the airways remain susceptible to asthma flare-ups. The person with asthma may have several asthma attacks after a first asthma attack has been triggered. This is sometimes called the second wave of asthma attacks. The subsequent attacks can actually be worse than the first attack that initiated the inflammation of the airways.