Dysbiosis

Dysbiosis refers to an imbalanced gut microbiome — reduced microbial diversity, loss of beneficial species, and/or overgrowth of potentially harmful species. In the context of mast cell conditions, dysbiosis acts as both a cause and consequence of mast cell overactivation.

How Dysbiosis Increases Mast Cell Activation

• Increased Histamine-Producing Bacteria relative to Histamine-Degrading Bacteria → higher baseline histamine in the gut
• Reduced butyrate production → loss of mast cell-stabilizing signals + weakened epithelial barrier
• Increased Intestinal Permeability → bacterial products (LPS) crossing into the lamina propria → mast cell activation via Toll-like receptors
• Reduced DAO support — a damaged epithelium from dysbiosis-related inflammation produces less DAO

How Mast Cell Activation Causes Dysbiosis

• Mast cell mediators alter gut motility (diarrhea or dysmotility) → changes the physical environment bacteria live in
• Tryptase and other proteases damage the mucosal layer → loss of the niche that supports beneficial bacteria
• Chronic inflammation shifts the gut environment toward species that thrive in inflammatory conditions
• Changes in intestinal secretions (acid, mucus, bile acids) alter the chemical environment

This bidirectional relationship creates another self-perpetuating loop within The Gut-Brain-Mast Cell Axis.

What Causes Dysbiosis

Antibiotics (especially broad-spectrum), chronic stress, low-fiber diets, chronic inflammation, PPIs (proton pump inhibitors), and the inflammatory environment of active mast cell disease itself. The implication: improving the microbiome in the context of active MCAS may require simultaneous mast cell stabilization — trying to fix the microbiome while mast cells are constantly disrupting it is an uphill battle.