We thank Lange et al for their comments. They have raised an important issue about airborne endotoxin exposure in occupational chronic cough. We reported that airborne endotoxin, as well as antigens from mushroom spores, was one of the important causes of cough in mushroom workers. As Lange et al have suggested, the phenomenon occurring in the mushroom farm workers is similar to that in cotton textile workers (byssinosis). Actually, some mushroom workers noticed cough in the first 2 weeks. This seems too short a time in which to be sensitized by mushroom spore antigens, therefore, we think that the cough resulted from exposure to chemicals, for example, endotoxin. As stated in our report, the latent time period from the start of working to the onset of symptoms of organic dust toxic syndrome (average, 1.8 months) was the shortest, the second was eosinophilic bronchitis (average, 3.5 months) and the third was cough-variant asthma (average, 4.1 months). However, we recently have seen two cases of hypersensitivity pneumonitis due to another kind of mushroom spore in which the latent period was only 2 months in one patient1–
and 3 months in the other (unpublished data). Based on these cases, 3 months might be enough time to be sensitized by mushroom antigens, in which case all 71.4% of workers reporting chronic cough that developed within 3 months after the start of employment might not be the result of endotoxin inhalation alone. We speculate that a high concentration of airborne mushroom spores may shorten the sensitization period in the contemporary mushroom farm worker. Thirty percent of workers were sensitized to the spore in the first year and 93% in the second year.2
We are now developing a system for measuring serum IgG and IgE levels in response to the spore antigens in our laboratory.