Extrinsic allergic alveolitis due to rat serum proteins

In a research assistant with recurrent episodes of extrinsic allergic alveolitis on exposure to rats, typical systemic and pulmonary reactions on inhalation and positive reaction on prick testing were elicited only by tests with rat serum; precipitins were present against rat serum and rat pelt, but not rat fur, and were also present against rat urine, which may contain large amounts of serum protein and which may have been a main source of antigenic exposure.