Gluten intolerance includes versions of proteins that bind to the gliaden protein component of gluten. It is bound in a manner that optimally exposes the antigenic surface for the immune system to mount an immune response. In addition, the cells of the small intestine normally have "tight junctions" to limit passage of large particles into the blood stream. In gluten intolerant individuals, the immune response to gliaden provokes expression of "zonulin". The zonulin protein turns the tight junctions into "loose junctions". Larger particles in the digestive tract can pass into the blood stream. That expands the possibilities for expose of more antigens to the immune system.
There is a variant of the casein protein in Holstein sourced cow's milk that produces peptides with a morphine like structure when hydrolyzed by digestive enzymes. In a gluten intolerant individual, this morphine like substance can pass into the blood and produce a narcotic impact on the brain. The simple fix is to avoid gluten and dairy. Sometimes it is not so easy. Unintended exposure leads to a few days of extended trips to the "reading room".
There is a fascinating discovery of the difference between the A1 beta-casein variant, and the A2 beta-casein variant, as chronicled in the book “The Devil in the Milk” by Kenneth Woodward. Some line of cattle have A2 capability, but most have A1. Since it is a double allele thing, the possibilities are 100% A1, 50-50 A1 A2, or 100% A2. A2 milk is the ideal, which goats produce exclusively, but it can be bred into lines of cattle. BCM7 is the “devil” in our milk.