Bronchial lability and skin reactivity in siblings of asthmatic children.

Abstract

Children with asthma (42 boys and 33 girls; age range 4 yr 2 mo. to 15 yr) and 75 of their siblings (37 boys and 38 girls; age range 4 yr 3 mo. to 17 yr 8 mo.) were studied to elucidate the mechanisms involved in the increased asthma prevalence in boys, a prevalence that tends to disappear after puberty. Immediate cutaneous hypersensitivity to 5 allergens and maximum fall in peak expiratory flow rate after 6 min of treadmill running (bronchial lability) were determined in patients and siblings. There was no significant difference between boys and girls in skin test reactivity to single or multiple allergens in the sibling group. The percentage fall in peak expiratory flow rate after exercise was significantly greater in male than in female siblings, and when a positive test was defined as a fall after exercise of either 10 or 15% of the rate before exercise the number of positive tests was significantly greater in boys. More boys than girls in this age group have asthma because their bronchial lability is greater and not because more boys are atopic.