Prevalence of atopy and exercise-induced bronchial lability in relatives of patients with cystic fibrosis.

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. 