I had terrible GI symptoms. I went on a dairy free, gluten free, low anti-histamine diet. My PCP put me on omeprazole 40 mg and as long as I follow the diet strictly the stomach gut issues had calmed down considerably. My son has ME/CFS and when he was at his worst he had the same issues. As soon as his ME/CFS calmed down, the food sensitivities eventually went away.