March 14, 2023

Mast cell activation syndrome: What happens when histamine goes haywire

Check out our blog post on mast cell activation syndrome

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….

Symptoms of MCAS…

The symptoms of MCAS are varied and wide. Mast cells are in nearly every tissue in your body and cause an inflammatory response throughout your body, so a flare up can affect many systems of your body. While they are there to protect you they can cause harm if their activation is never turned off as in the case of atherosclerosis. Mast cells play a large role in the pathogenesis of plaque rupture due to the release of tryptase and chymase (proteases found at the rupture site) (Bot, I).

Symptoms of mast cell activation include but are not limited to:

  • hives, itching, swelling, flushing

  • nausea, vomiting, diarrhea, bloating, cramping

  • low blood pressure, vascular permeability/inflammation and swelling,

  • wheezing, shortness of breath, cough, mucous production, asthma

  • insomnia, brain fog, vertigo, headaches, lack of focus/concentration, pain

These symptoms may come and go. In the case of MCAS, mast cells are hypersensitive and there are a number of triggers that can send them into overdrive.

What triggers MCAS?

What your body responds to varies from person to person. Each person is unique in their exposures over their lifetime. It is the cumulative exposure and lack of tolerance that can illicit an activation. Some common triggers of mast cell activation are:

  • Environmental toxins like pesticides, phalates, molds, dust, pollen, heavy metals, plastics.

  • Smells: perfumes or cleaning agents.

  • Medications: anti-inflammatories, opiods, antibiotics, some supplements

  • Food: dairy, gluten, corn, soy, and foods high in histamine

  • Physical trauma: exercise, pain

  • Infection: viruses, fungi, parasites, and bacteria

How are infections and toxins related to MCAS?

Infections and toxins can be a trigger or a cause for mast cell activation syndrome. An initial infection will cause a mast cell response causing the infection to become dormant, but a chronic, low lying infection or re-activation can be a cause for continued mast cell stimulation. Some common infection triggers:

  • Epstein-barr virus

  • HHSV -6

  • Lyme disease

  • Mold colonization

  • Endotoxin release from leaky gut

  • Parasites

  • Candida

Toxins are also contributory to mast cell activation. Toxin exposure is cumulative, daily exposure and becoming more and more of problem as our world becomes more toxic. It is not a one-time, low dose exposure that stimulates immune activation but it is the cumulative effects over time that decrease oral tolerance which activates immune responses. Some examples of toxins:

  • water contamination with arsenic, lead, cadmium

  • mold exposure

  • pesticides

  • plastics

  • poor air quality

  • mercury

Toxins and infections cause the immune system to become ineffective. They do this by causing low level inflammation, chronic production of immune mediators, and depressed natural killer cell and T-cell function (Costenbader, K.H). This all leads to the mast cells going into overdrive!

So what can you do?

The treatments for MCAS are aimed to calming the mast cells down to reduce the inflammation they cause to allow your immune system to work as it should. A few things that are shown to be effective:

  1. Eat a low histamine diet

  2. Incorporate antihistamine and mast cell stabilizing foods into your diet: vitamin c, bromelain, stinging nettle, probiotics, raw honey, onions, berries, turmeric

  3. Identify triggers

  4. Increase detoxification: sweating, epsom salt baths, daily bowel movements

  5. Get your gut in line! The gut contains the G.A.L.T
    (gut associated lymphoid tissue) which houses 70% of your immune system!

  6. Get good sleep

  7. Reduce stress

Are you concerned about mast cells? Schedule a wellness consult to get to the root of your concerns!


Bot I, Shi GP, Kovanen PT. Mast cells as effectors in atherosclerosis. Arterioscler Thromb Vasc Biol. 2015 Feb;35(2):265-71. doi: 10.1161/ATVBAHA.114.303570. Epub 2014 Aug 7. PMID: 25104798; PMCID: PMC4304944.

Costenbader, K.H., Karlson, E.W. Epstein–Barr virus and rheumatoid arthritis: is there a link?. Arthritis Res Ther8, 204 (2006).

Krystel-Whittemore M, Dileepan KN, Wood JG. Mast Cell: A Multi-Functional Master Cell. Front Immunol. 2016 Jan 6;6:620. doi: 10.3389/fimmu.2015.00620. PMID: 26779180; PMCID: PMC4701915.

Urb M, Sheppard DC. The role of mast cells in the defence against pathogens. PLoS Pathog. 2012;8(4):e1002619. doi: 10.1371/journal.ppat.1002619. Epub 2012 Apr 26. PMID: 22577358; PMCID: PMC3343118.

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