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Mast cell activation syndrome: What happens when histamine goes haywire

What are mast cells?

Mast cells, simply put, are the alarm system for your immune system to fire up to an invader or trigger. Mast cells contain inflammatory cytokines, leukotrienes, proteases, prostaglandins and histamine.

When mast cells are stimulated from a foreign invader or trigger they de-granulate and release their inflammatory mediators activating your immune system. They are designed to protect you so they are located in areas that are prone to invasion: skin, lungs, gastrointestinal tract (Urb M). They are an important component of your adaptive and innate immune system. One place they are highly concentrated in is the gut because this is a path for many bacteria, viruses, and parasites to enter the body.

Mast cells regulate of variety of physiological functions, including vasodilation, angiogenesis, bacterial, and parasite elimination (Krystel-Whittemore M). When a mast cell de-granulates the inflammatory mediators are released which can result in a wide array of symptoms for the host.

What symptoms occur when mast cells de-granulate?

Since mast cells reside in areas of the body that are prone to invasion they are one of the first cells to respond to an invader. They pull the alarm and activate other immune cells to come to the area causing vasodilation, increased vascular permeability, and your bronchials (airways) and smooth muscle to contract or tighten.

Under normal conditions this is healthy. Under normal conditions the mast cells will activate the immune system, kill the invader, turn off, and the inflammation is then cleaned up and the response does not happen again until the next invasion. Mast cell activation syndrome (MCAS) is different....

What is mast cell activation syndrome?

In MCAS, your mast cells are over-reacting. They release too many inflammatory mediators too often. Why does this happen? Let's first look at the symptoms of MCAS....