The hygiene hypothesis states that a lack of exposure to microorganisms—both beneficial and potentially harmful—during early childhood increases susceptibility to development of allergic diseases by creating an imbalance in immune system development. Brenda has blogged on the topic before, and I’ve blogged about immune balance.

A recent study published in the Journal of Allergy and Clinical Immunology has found that gut diversity in infancy helps protect against the development of allergies.1 The study involved 40 children: 20 with atopic eczema, and 20 children with no health conditions. Stool samples were collected from each child at one month and twelve months of age, and the DNA of bacteria present in the infants’ guts was identified. The diversity of gut microflora at one month of age was significantly greater in the healthy children than in those children who later developed allergies.

The researchers suggested that in the absence of stimuli from a diverse array of microbes, the immune system may overreact against harmless antigens in the environment, such as food. I have blogged on the topic of food sensitivities, as well, highlighting the importance of maintaining immune balance with a good balance of gut bacteria.

So how do infants acquire gut bacterial diversity? First, by vaginal delivery, through which they are inoculated with protective bacteria from their mother (which works best if mom is on a plant-based diet, eating prebiotic foods, and taking probiotics throughout the pregnancy); second, by breastfeeding, which delivers yet more beneficial bacteria and prebiotics to feed the beneficial bacteria establishing in the baby’s gut; three, without the use of unnecessary antibiotics, which decrease gut bacterial diversity; and four, with a healthy diet consumed by the mother. When any of these factors cannot be optimized, probiotics formulated for infants can help build the beneficial bacteria in the gut.


  1.  T.R. Abrahamsson, et al., “Low diversity of the gut microbiota in infants with atopic eczema.” J Allergy Clin Immunol. 2011 Dec 6. [Epub ahead of print].