I do not know about leaky gut syndrome. I do know that some kids do not tolerate milk or certain kinds of sugars other than lactose. Even though you have eliminated milk, it is hard to get rid of all dairy products because they are found in so many foods as are some of these other sugars and, as below, wheat. The reason I was writing this was to ask about celiac disease. There have been quite a number of people with GBS/CIDP and celiac disease. Celiac is sensitivity to gluten such as found in wheat. It is pretty common and can be tested for with a blood test. It is not common in children, but because it is associated with this and other autoimmune diseases, it might be worth asking about.