Extrinsic allergic alveolitis caused by a cold water humidifier.

Three workers developed classical extrinsic allergic alveolitis while working in a printing works that had a contaminated cold water humidifier. All had nodular shadows on their chest radiographs, reduced gas transfer measurements, and lung biopsy specimens that showed an alveolitis with giant cells and cholesterol clefts. In two subjects bronchoalveolar lavage was performed and the lavage fluid contained more than 70% lymphocytes in each case. Bronchial provocation tests with the humidifier antigen in these two workers reproduced their symptoms. Unlike previously reported cases, where exposure was to humidifiers working at generally higher temperatures, challenge with thermophilic actinomycetes in our two patients produced no reaction. Tests for precipitins to the humidifier antigen gave strongly positive reactions in the three workers but no single organism isolated from the humidifier produced a significantly positive reaction.