Research from Germany suggests that longer duration of breastfeeding decreases the risk of allergies in early childhood, especially in children of mothers without a family history, and proposes a mechanism which may explain the protective effect.

The concentration of soluble CD14, which plays an important role in innate immunity, in the breastmilk of mothers of 803 babies was measured at 6 weeks post-partum. The incidence of atopic dermatitis and asthma was recorded over the following 2 years.

The lowest incidence of dermatitis in children of mothers without a history of atopic diseases was found among those breastfed for 6 to 9 months. There was also an inverse association between duration of breastfeeding and risk of asthma (P=0.01). The protective effect of breastfeeding was synergistic with soluble CD14 concentrations in breast milk (P for trend 0.0005).

Rothenbacher D et al (2005). Breastfeeding, soluble CD14 concentration in breast milk and risk of atopic dermatitis and asthma in early childhood: birth cohort study. Clin Exp Allergy 35: 1014-21.