Abstract
Skin tests and exercise tests were performed on children with cystic fibrosis (CF) and first-degree relatives of CF children. Positive skin tests were found in 56% of patients and 19% of relatives, but the prevalence of atopy in CF patients bore no relationship to its prevalence in their relatives. Increased 0ronchial lability, mainly due to bronchoconstriction, was present in 54% of patients and 27% of relatives. The results showed that increased prevalence of bronchial lability, but not atopy, is found in first-degree relatives of CF children, and that the abnormal lability and atopy found in CF children does not indicate a familial allergic background.