his below was written by Dr. McCandless who is using LDN in autistic kids and some adults with various autoimmune diseases. She has many kids on LDN who have terrible gut issues and until the gut is cleaned up her kids will experience negative side-effects on LDN, this may also be why many MS'ers FAIL LDN.
I found this from a doctor explaining why LDN sometimes fails.
What I have found out is that the response is
better for those taking LDN who remove casein and
gluten and sometimes soy also from their diets. As
naltrexone is an opioid antagonist, some of these
large peptides in wheat and milk create opioid-like
compounds in the brain and gut, and even the tiny bit
of naltrexone in the low-dose form can cause some problems.
I have almost all my gut kids on good probiotics and many also on
digestive enzymes to help absorption issues, and absolutely forbid any refined sugar (encourages yeast).