Department of Occupational and Environmental Health, Stockholm County Council, National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden. 

BACKGROUND: The evidence for a preventive effect of breast-feeding on the development of eczema in childhood remains controversial. OBJECTIVE: To investigate the effect of breast-feeding in various phenotypes of eczema to 4 years. METHODS: A birth cohort of 4089 children made up the study base. Data on breast-feeding, allergic symptoms, and potential confounders were obtained from questionnaires when the children were 2 months and 1, 2, and 4 years old. At 4 years, blood specific IgE was analyzed. Children with symptoms of eczema and asthma during the period of breast-feeding were excluded in most analyses on risk assessment of eczema and asthma, respectively, to avoid disease-related modification of exposure. RESULTS: Exclusive breast-feeding for >or=4 months reduced the risk for eczema at the age of 4 years (odds ratio [OR], 0.78; 95% CI, 0.63--0.96) irrespective of combination with asthma, sensitization to common allergens, or parental allergic disease. This decreased risk was most evident for children with onset of eczema during the first 2 years persisting to 4 years (OR, 0.59; 95% CI, 0.45--0.77). Among children with early-onset eczema, irrespective of persistency, followed by late onset of asthma or early-onset asthma irrespective of persistency, followed by late-onset eczema to 4 years, a protective effect of breast-feeding was also seen (OR, 0.48; 95% CI, 0.30--0.76). CONCLUSION: Breast-feeding 4 months or more reduces the risk for eczema and onset of the allergy march to age 4.