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? How do I use Histamine Block? Practitioner Directory Are there any warnings or side effects of using Histamine Block? Comments 0 comments Article is closed for comments.