Respiratory infection, exposure to mouse allergen and breastfeeding: role in recurrent wheezing in early life.

BACKGROUND: Environmental factors may influence the development of allergen sensitization and asthma. The aim of this study was to evaluate the role of endotoxin and allergen exposure in early life as a risk factor for recurrent wheezing.

METHODS: One hundred and four infants from low-income families, at high risk of asthma, were enrolled at birth. Dust samples were collected from the bedding and bedroom floor within 6 months after birth. Recurrent wheezing was defined as 3 or more wheezing episodes in the past year. Endotoxin was determined by Limulus amebocyte lysate assay, and major indoor allergens were quantitated by ELISA in dust extracts. IgE antibodies were measured by ImmunoCAP at 30 months of age.

RESULTS: At 30 months, 51 of the 99 infants who completed the study (51.5%) had recurrent wheezing. Respiratory infection was strongly associated with recurrent wheezing (OR 6.67, 95% CI 1.96-22.72), whereas exclusive breastfeeding for at least 1 month was a protective factor (OR 0.09, 95% CI 0.01-0.51). Exposure to high levels of mouse allergen was more frequent among non-recurrent wheezers, approaching significance (OR 0.12, 95% CI 0.01-1.13; p = 0.064). None of the children were sensitized to mouse. Sensitization to mite was found in 26/90 (28.8%) children, with no association with recurrent wheezing.

CONCLUSION: Respiratory infection was strongly associated with recurrent wheezing in the first 30 months of life, in children at high risk of asthma, living in a socially deprived community in Brazil.