Inflammation is a complex process of protecting the body. This very general defense mechanism is triggered by various harmful stimuli, such as pathogens, damaged cells or inhalation of irritants. During this process, so-called inflammatory immune cells will migrate to the site of the inflammation. The function of inflammation is to remove the initial cause of the cell damage, necrotic cells and tissues damaged by the initial stimulus and the inflammatory process itself, as well as initiate tissue repair. Inflammation may be acute, i.e. temporary, or chronic and therefore persist for a long time. More often than not, this chronic inflammation will progress to fibrosis of the lung tissue, which will alter pulmonary function.

The causes of chronic pulmonary inflammation are manifold. This may include inhalation of environmental pollutants or substances in the workplace (asbestosis or silicosis) and exposure to certain gases. Inhalation of dust contaminated by bacterial, fungal or animal sources and smoking also cause inflammatory cells to appear in the lungs.  Some inflammatory pulmonary diseases such as sarcoidosis have an unknown origin. Finally, certain lung infections, such as infections with mold of the genus Aspergillus, cause allergic bronchopulmonary aspergillosis, characterized by chronic allergic pulmonary inflammation and fibrosis of the lung tissue.

It is a type of inflammation characterized by the appearance of specific immune cells. These lead to the development of pulmonary allergic symptoms (wheezing, chest tightness, difficulty breathing, bronchoconstriction), which is then referred to as asthma. Allergic pulmonary inflammation is stimulated by the penetration of allergens into the lungs. The most common allergens are pollen, dust mites, animal hair and mould spores. Chronic low-dose stimulation of the lungs by allergens induces chronic inflammation and, ultimately, fibrosis of the lung tissue and decreased respiratory capacity.