Family structure, neonatal infection, and hay fever in adolescence

11,765 babies born since 1975 in Sheffield have been visited by a health visitor at one month of age to identify those at risk of sudden infant death. The authors describe a longitudinal study created by linking these health visitor records to data from a survey from allergic disease among teenagers throughout Sheffield. A history of hayfever and family structure was obtained via postal questionnaire. 723 children underwent skin prick testing with mixed grass pollen extract. The prevalance of hay fever was reduced (p<0.0001) among children of younger mothers and those from larger families. The number of older siblings exerted a stronger effect than the number of younger siblings. Infants breastfed exclusively during the first month were at higher risk (p<0.05) of subsequent hay fever. Adolescents at higher risk of hay fever by virtue of their family structure were more likely to be sensitised to grass pollen (p<0.002). No significant relationships occurred between hay fever and infection in the first month after birth