I had some GI issues. After a 3rd endoscopy and results showing hypertrophic cells, I was told to stop taking a prescription med I had been on. On my own, in trying to figure out what I was dealing with. I omitted dairy, sugar and gluten products. And I also chose as many organic products as possible. Nonorganic fruits and vegetables are sprayed with glyphosate. After 2 weeks. I started feeling much better. So, I knew I was on to something. Find a doctor that will test for the CAUSE of your son’s issue. It could be SIBO (small intestinal bacterial overgrowth), a fungus, a parasite, mold. All these can be tested for.
Best of luck to you and your son.