What are the active ingredients in Histamine Block sourced from? Ceylon Keeslar November 17, 2020 01:39 Updated Follow Diamine oxidase is derived from porcine (pig) protein concentrate. Vitamin C is from non-GMO corn. Related articles Does Histamine Block contain gluten or grains? Why is Histamine Block not suitable for vegetarians or vegans? Are there any warnings or side effects of using Histamine Block? How do I use Histamine Block? Practitioner Directory Comments 0 comments Article is closed for comments.