hypersensitivity pneumonia

Hypersensitivity pneumonitis is a group of lung conditions caused by an allergic reaction to inhaled substances. When exposed to these agents, the lungs become sensitized. Re-exposure triggers an acute inflammation of the smaller airways and alveolar walls, potentially leading to airflow obstruction. Chronic cases can result in granulomas and widespread lung fibrosis, causing lasting respiratory impairment.1

A common example is farmer's lung, caused by inhaling moldy hay spores. This can lead to fever, breathlessness, and cough. Other forms include pigeon breeder's lung, triggered by proteins from birds, and conditions linked to mushroom cultivation or exposure to redwood sawdust. "Humidifier fever" is another variant, caused by molds in humidifier systems. Avoiding the offending dusts is the most effective treatment.12