The neonatal period is a critical time with regards to priming the gut for allergic disease. After birth the intestinal barriers and immunoregulatory networks are poorly developed and the post-natal period is a time for the normal commensal microbial flora to develop. The timing and dose of dietary antigens is imperative in this development. The mucosae are bombarded immediately after birth by a large variety of microorganisms as well as protein antigens from the environment. The mucosal surface is huge, 200 times the surface of the skin.