Food allergies impact 6-8% of children in the U.S. Among them, peanut allergy is the most common cause of fatal and near-fatal food allergic reactions and is rarely outgrown. Its prevalence has steadily increased in children to over 1% during the past couple of decades. There is a more modest increase in other food allergies, including cow's milk, egg, wheat, tree nut, fish and shellfish allergy. The exact mechanisms contributing to the increase in food allergies are unknown. However, the infant microbiome and perinatal environmental factors, including farming vs. urban life-style, infant and maternal diet, immune status and breastfeeding may play a critical role.
Dysbiosis has been shown to precede the development of atopic dermatitis and food allergy, which typically initiate the “atopic march”, i.e. the progression to allergic rhinitis and asthma later in life. The infant gut microbiome is initially dominated by Bifidobacteria, especially in breastfed infants, due to human milk oligosaccharides that do not serve as fuel for the host but for the microbiome. By two years of age, the gut microbiome starts to resemble adult-like microbiome. This time frame coincides with is a rapid development of the immune system and presents a critical window of opportunity for prevention of allergic diseases.