Qualitative and quantitative differences in exposure may explain these contradictory findings. Several studies have demonstrated IgE responses against various types of wood including pine [12, 13]. However, in most of these studies, only few workers showed positive responses [12]. Allergy to pine dust is, therefore, unlikely to explain the elevated prevalence of atopy in the workers exposed to high levels of green dust. Also, it is unlikely to be related to pollen exposure, since the pine pollen skin-prick test results were not associated with exposure (data not shown).