What are the active ingredients is Histamine Block derived from? Ceylon Keeslar October 31, 2019 17:15 Updated Follow Diamine oxidase is derived from porcine (pig) protein concentrate. Vitamin C is from non-GMO corn. Related articles Does this product contain gluten, soy, or grains? Is HistaminX suitable for vegans and vegetarians? If not, why? Is this product vegetarian/vegan? How do I take this product? Practitioner Directory Comments 0 comments Article is closed for comments.