For those unfamiliar with Dr. Natasha Campbell-McBride, here is a brief excerpt from her book that I believe should be marked as 'for the protein intolerance diagnosed in the United States'.
"People with food allergies and intolerances should go through the Intro Diet in order to heal and seal their gut lining. The reason for allergies and food intolerances is a so-called 'leaky gut' when the gut lining is damaged by abnormal micro flora. Foods do not get the chance to be digested properly before they get absorbed through this damaged wall and cause the immune system to react to them. Many people try to identify which foods they react to. However, with damaged gut wall they are likely to absorb most of their foods partially digested, which may cause an immediate reaction or a delayed reaction (a day, a few days, or even a couple of weeks later). As these reactions overlap with each other, you can never be sure what exactly you are reacting to on any given day. Testing for food allergies is notoriously unreliable: if they had enough resources to test twice a day for two weeks, they would find that they are "allergic" to everything they eat. As long as the gut wall is damaged and stays damaged, you can be juggling your diet forever, removing different foods and never getting anywhere. From my clinical experience, it is best to concentrate on healing the gut wall with the Introduction Diet. Once the gut wall is healed, the foods will be digested properly before being absorbed, which will remove many food intolerances and allergies."
Dr. Campbell-McBride has been in practice with this philosophy of medicine since 1998.
At Ellie's last GI appointment, our fantastic and up-to-date doctor (he really is wonderful) told us there was some 'new' information coming out that speculated that a leaky gut caused additional proteins in to the body that caused reactions such as those of FPIES.