A parental history of asthma is a risk factor for wheezing and nonwheezing respiratory illnesses in infants younger than 18 months of age.

The relationship between respiratory infection and allergy as risk factors for the development of wheezing illnesses in infants has been in dispute. We hypothesized that a parental history of allergic diseases would be associated with an increased rate of respiratory infections as well as an increased rate of wheezing during infectious episodes. We prospectively evaluated 1,193 infants from birth to 18 mo of age, using bi-weekly telephone surveillance to document all respiratory events. The overall rate of respiratory illness (all RI) increased to a maximum of 10.6 illnesses/infant/year in the 7- to 9-mo age group and then leveled off in the older infants. Multivariable models adjusting for demographic variables, breast feeding, month of illness, number of siblings, and attendance at day care showed an increase in the rate of all RI in infants older than 7 mo of age who had a parental history of asthma (OR = 1.24, CI = 1.09 to 1.41) or a parental history of atopy (OR = 1.14, CI = 1.03 to 1.26). The rate of lower respiratory illnesses accompanied by wheezing was related only to a parental history of asthma (OR = 2.06, CI = 1.36 to 3.11). We conclude that all RI, most of which represent viral infections, are increased in otherwise normal infants with a parental history of asthma or atopy, whereas wheezing is related only to a parental history of asthma.