Lack of evidence for a protective effect of prolonged breastfeeding on childhood eczema: lessons from the International Study of Asthma and Allergies in Childhood (ISAAC) Phase Two

Background Exclusive breastfeeding for at least 4 months is recommended by many governments and allergy organizations to prevent allergic disease. Objectives To investigate whether exclusive breastfeeding protects against childhood eczema. Methods Study subjects comprised 51 119 randomly selected 8-to 12-year-old schoolchildren in 21 countries. Information on eczema and breastfeeding was gathered by parental questionnaire. Children were also examined for flexural eczema and underwent skin prick testing. Odds ratios (ORs) were calculated for each study centre and then pooled across populations. Results There was a small increase in the risk of reported 'eczema ever' in association with 'breastfeeding ever' and breastfeeding < 6 months [pooled adjusted OR 1.11, 95% confidence interval (CI) 1.00-1.22 and OR 1.10, 95% CI 1.02-1.20, respectively]. There was no significant association between reported 'eczema ever' and breastfeeding > 6 months (pooled adjusted OR 1.09, 95% CI 0.94-1.26). Risk estimates were very similar for exclusive breastfeeding < 2 months, 2-4 months and > 4 months and for eczema symptoms in the past 12 months and eczema on skin examination. As for more severe eczema, breastfeeding per se conveyed a risk reduction on sleep disturbed eczema (pooled adjusted OR 0.71, 95% CI 0.53-0.96), but this effect was lost where children had been exclusively breastfed for > 4 months (pooled adjusted OR 1.02, 95% CI 0.67-1.54). Allergic sensitization and a history of maternal allergic disease did not modify any of these findings. Conclusions Although there was a protective effect of ever having been breastfed on more severe disease, we found no evidence that exclusive breastfeeding for 4 months or longer protects against eczema. Our results are consistent with findings from a recent systematic review of prospective studies. The U. K. breastfeeding guidelines with regard to eczema should be reviewed. Intervention studies are now required to explore how and when solids should be introduced alongside breastfeeding to aid protection against eczema and other allergic diseases.