Inhalation and skin tests with extracts of hay and fungi in patients with farmer's lung.

Farmer's lung is a specific respiratory illness which results from the inhalation of mouldy hay, grain, straw, or other similar vegetable matter. Hay becomes mouldy if it is harvested and stored wet. Fungi and bacteria multiply in it, fermentation occurs, and heat is produced. When dry, the mouldy hay is partly converted to a fine dust. The illness was described by Campbell in 1932 and later by Fawcitt (1936a and b, 1938a and b), Fuller (1953), Studdert (1953), Frank (1958), and Dickie and Rankin (1958). It is fairly common in Britain (Staines and Forman, 1961). Acute, subacute, and chronic phases of the illness have been described by Fuller (1953). The acute illness is characterized by dyspnoea, cough, fever, malaise, cyanosis, basal crepitations, and later diffuse reticulo-nodular chest radiographic shadowing. The pulmonary histological changes consist of a granulomatous infiltration of the interstitial tissues with no evidence of bacterial or fungal proliferation. Later pulmonary fibrosis, distortion of the bronchioles, and emphysema occur (Fuller, 1953 and 1958; Frank, 1958; Dickie and Rankin, 1958; Totten, Reid, Davis, and Moran, 1958; Seal, 1962). The acute symptoms which occur after exposure to mouldy hay have been attributed to a bronchomycosis (Fawcitt, 1936a and b; Tornell, 1946), mechanical blockage of the pulmonary airways by the swelling or germination of fungal spores (Williams and Mulhall, 1956; Pickworth, 1961), non-specific pulmonary irritation (Studdert, 1953), the toxic effect of a mould in a non-allergic person (Frankland and Hamilton, 1958), a hypersensitivity reaction to fungi or their products (Fawcitt, 1938a and b; Dickie and Rankin, 1958; Cooper and Greenaway, 1961), the physical, chemical, or immunological properties of the fine degraded hay fibre which has been acted on by the mouldy hay microflora (Duncan, 1945), and the inhalation of bacterial endotoxins (Pernis, Vigliani, Cavagna, and Finueli, 1961). This report describes skin and inhalation tests with crude hay and extracts of hay and fungi on patients with farmer's lung and other conditions. The purpose of the investigation was twofold: to investigate the relation between exposure to hay dust and symptoms in patients thought to be suffering from farmer's lung, and to obtain new information on the aetiology, pulmonary physiology, treatment, and diagnosis of the condition.