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Why can repeated allergic reactions to organic dusts lead to pulmonary fibrosis?

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Asbestosis — occupational disease The lung disease asbestosis is caused primarily by prolonged inhalation of asbestos fibers. It occurs mainly among workers whose occupations involve exposure to asbestos and people who live near mines, factories, and construction sites.

Repeated allergic reactions to organic dusts can lead to pulmonary fibrosis through a process of chronic inflammation known as hypersensitivity pneumonitis.

When individuals are repeatedly exposed to organic materials—such as fungal spores from moldy hay, bird droppings, or other organic dusts—their lungs undergo a recurring allergic inflammatory response. This process involves the sensitization of the lung tissue and the development of inflammation in the smaller bronchioles and alveolar walls.12

Over time, these repeated episodes of inflammation cause the body to replace normal, elastic lung tissue with dense, fibrous connective tissue. This scarring, or fibrosis, stiffens the lungs, reduces the space available for air, and impairs the ability of the lungs to exchange gases. If the exposure continues, this damage can progress to chronic respiratory impairment and, in severe cases, respiratory failure. The most effective way to prevent this progression is to avoid further exposure to the offending dusts.3412