Asthma and wheezy bronchitis in children. Skin test reactivity in cases, their parents and siblings. A controlled population study of sex differences.

Twice as many boys as girls are prone to wheeze (15-3% compared with 7%). This study examines the possible immunological basis for this phenomenon. There were 1064 children in this survey. The family of each wheezy child was indexed, and a control sample of families was selected. At least 85% of the study population were skin tested for Type 1 allergic reactions. An interval survey of values for FEV1, FVC and PEFR against height was completed. Of 118 wheezy subjects there were 83/542 boys and 35/522 girls. Single and multiple sensitivity, the capacity to react to two or more major allergens, is examined. Of the child asthmatics, significant differences from controls emerge for pollens, foods and the house dust mite. These differences are borne out with multiple sensitivity. (P greater than 0-001.) Of the brothers and sisters of asthmatics, only the sisters show differences from controls. This is true for grass pollen, cow's milk and the house dust mite, and also to a highly significant degree for multiple sensitivity (P greater than 0-001). When the incidence of multiple sensitivity is expressed for all children in the asthma group, that is, cases and their siblings, the sex difference is not demonstrable. The mothers (P greater than 0-05) and fathers (P greater than 0-01), of asthmatics also differ from control parents in respect of skin sensitivity. If multiple sensitivity is equated with atopy, it may not be the main determination of the capacity to wheeze, and thus of the sex difference. The mean curve for interval PEFR for asthmatic children was significantly lower than that of control children and of the brothers and sisters of asthmatics.