[Extrinsic allergic alveolitis of occupational origin].

Occupational factors encountered in farming and other agricultural activities produce a particular risk for respiratory diseases. For some, such as extrinsic allergic alveolitis, diagnosis depends upon a range of epidemiological, clinical, radiological and immunological arguments. Farmer's lung is one of the most common form of extrinsic allergic alveolitis. Bird breeder's lung is another, the list is long. The environmental allergens likely to affect alveoli and interstitial tissues have been identified, but simple detection of antibodies does not constitute a pathognomonic criterion of extrinsic allergic alveolitis. Co-immuno-electrodiffusion is a rapid and sensitive technique for the demonstration of remarkable precipitating systems of extrinsic allergic alveolitis. This investigation enables subjects who really have the disease to be distinguished from contact subjects. Diagnosis is important to prevent development of a disabling and irreversible pulmonary fibrosis.