08/20/2026
With MCAS, what came first: the gut problem or the immune system problem?
Sometimes we know, and sometimes we do not. What we do know is that the gut and immune system can start feeding each other. Mast cells sit right under the gut lining, and when they become activated they can release histamine, prostaglandins, tryptase, and other inflammatory signals that affect gut motility, intestinal permeability, and nerve signaling.
Once that gut environment starts changing, the nervous system and immune system respond to those changes too. Now the gut can influence the immune system, the immune system can influence the gut, and the feedback loop keeps building.
That is why with MCAS I do not want to only ask, “How do we lower histamine?” I want to know why those mast cells are being stimulated in the first place and what is keeping that reaction going.
🧩 MCAS is not one isolated problem. The goal is to understand the whole conversation happening between the gut, immune system, and nervous system.