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Histamine Intolerance Part 7 What is Mast Cell Activation Syndrome?

20 September 2022


What is Mast Cell Activation Syndrome?


Mast Cell Activation Syndrome (also called MCAS) is complex. Still, we can tell you that MCAS is one cause of many people's HIT (histamine intolerance).


This year, I learned that I have HIT and am still trying to figure out if I also have MCAS (just quietly, I think I might as I'm bloody sensitive to everything)!

I should live in a bubble.


MCAS is an immune disorder and form of mast cell disease. This illness is characterised by high levels of mediators. The mast cells release mediators (such as histamine) when they shouldn't. These cells are over-responsive.


Everything I am learning is being turned into information for you or anyone curious about this stuff. This information will also be available soon on my podcast and in my book, so stay tuned for that.


Mast cells are only something I just discovered and MCAS, so I'm still trying to get my head around it all. It is all quite complicated and intricately connected.


Health is fascinating and can also feel frustrating as we navigate these complexities. 


Doctors rarely recognise MCAS because very few doctors are aware of its symptoms and may dismiss it altogether. This is unfortunate but luckily, holistic doctors do know about it.


What are Mast Cells, and Why Do They Get Activated?


Mast Cell. Source:Allergic Child.com

 This is a mast cell. These cells are responsible for both causing allergic reactions and anaphylaxis but also but also healing wounds and defending the body against pathogens.


A Mast cell is a type of immune cell (white blood cell) that stores inflammatory mediators such as histamine. They are also responsible for housing other chemicals such as leukotrienes, prostaglandins, tryptase, cytokines and reactive oxygen species.

Histamines are the most commonly known.


These cells are found in a person's blood vessels, brain, bone marrow, skin, tendons, respiratory tract, GI tract, urinary tract, organs of the reproductive system and surrounding nerves.


Mast cells can also be found in the blood when infections or diseases occur. When the threat of infection is gone, the mast cells work to repair the tissue.


Allergic reactions in humans involve mast cells, but it does not mean someone with allergies will always have MCAS (we will discuss this soon).


When someone has MCAS, they may find that many factors can trigger a negative response. One of those responses is often a buildup of histamine (HIT).


Some Symptoms Linked to MCAS

  • A rash or hives (urticaria)
  • Itchy skin or crawling sensation
  • Heart palpitations/irregular heartbeat
  • Low blood pressure
  • Headache or even migraine
  • Tightness in the chest
  • Changes to weight (losing or gaining)
  • Digestive issues (nausea, vomiting, diarrhoea)
  • No appetite or very little
  • Anxious feelings
  • Vision changes
  • Fatigue
  • Feeling weak
  • Feeling dizzy

What can be confusing is that these symptoms can also be the same as HIT. I told you it is complex, didn't I?


How to Differentiate?


With HIT (histamine intolerance), this is often food-related. When we add foods that contain histamine, they can cause a buildup of histamines in the body (when someone has trouble breaking them down).


If someone has trouble breaking down histamine, they may also have trouble with histamine-liberators and DAO-blocking beverages such as coffee, tea and alcohol.


We discuss this in greater length in our other HIT blog here.


MCAS, on the other hand, has a different cause. This issue relates to a person's immune system and histamines (stay with us here). You see, the mast cells don't just release histamine. Mast cells also release other proinflammatory molecules. 


This flood of proinflammatory chemicals can have a cascading effect on the body. One of these effects is HIT. It is confusing, that's for sure!


So you may have HIT on its own, or you may have MCAS that causes HIT. Determining what is true for you will help you immensely!


Work with a good integrative/functional doctor or naturopath. Ensure you get the proper testing and work out the correct protocol.


We give some suggestions for HIT-friendly probiotics and other supplements throughout our other blogs (see all links in the blog footer).


Factors that Cause MCAS


Various factors can trigger Mast Cell Activation Syndrome, such as:


  • Environmental Toxins (heavy metals*, chemicals, EMF)
  • Environmental Factors (extreme temperatures
  • Emotional aspects (intense/chronic stress and anxiety)
  • Co-infections (mould, Lyme etc.)
  • Insect bites (mosquitos, sand flies, wasps, hornets etc.)
  • Medicines/pharmaceuticals that liberate histamine or block DAO enzyme production (DAO is one of the enzymes that breaks down histamine)
  • Anesthetics
  • Preservatives in food and beverages (especially sodium benzoate)
  • Smoke of any kind can be a trigger. 
  • Cleaning Products (use natural or make your own)
  • Laundry Products (avoid commercial and avoid fabric softener and dryer sheets)
  • Room sprays, synthetic fragrances and scented candles (diffuse pure essential oils instead)
  • Personal fragrances (body sprays, perfumes) use natural essential oils instead. 
  • Fake tan (sorry, but this is incredibly toxic on many levels as it absorbs into your blood and system)
  • For women, personal care products (this list is long), opt for natural body care, hair care, makeup and tampons/pads made with certified organic cotton.
  • Bath and shower products
  • Feminine douches 
  • High histamine foods (see our blog here)

*Heavy metals such as aluminium, arsenic, bismuth, cadmium, lead and mercury can be especially problematic as they're known to destabilise mast cells.


MCAS is not to be confused with mastocytosis. Mastocytosis is a mast cell disease where abnormal mast cell growth is present. Mast cells build up under the skin and cause massive skin rashes, GI problems and bone pain.


If you have HIT and MCAS, you will probably have histamines accumulate quickly in your body. You will need to be more diligent about your environment and health and manage your triggers with absolute care.


Are there Any Other Issues Related to MCAS?


Yes, there are many! (some of these have already been mentioned) such as;

  • Allergies/Asthma (or both)
  • Autism
  • Autoimmune conditions (Hashimoto's, Lupus, MS, RA)
  • EDS (Ehlers-Danlos Syndrome)
  • CFS (chronic fatigue syndrome)
  • CIRS (Chronic Inflammatory Response)
  • Fibromyalgia 
  • Infertility (endometriosis)
  • Interstitial Cystitis
  • Coeliac disease
  • Eosinophilic esophagitis
  • Food allergies/food intolerances
  • Gastroesophageal reflux
  • Headaches and migraines
  • IBS (irritable bowel syndrome)*
  • Mood disorders (severe mood changes/depression/anxiety)
  • Multiple Chemical Sensitivities
  • POTS (postural orthostatic tachycardia syndrome)
  • Tinnitus


*IBS can be caused by SIBO (small intestinal bacterial overgrowth)


What Causes MCAS?


Still, the actual cause can be different (some are exogenous, and some are endogenous). Some of these are both causes and also triggers. So we chatted about what can start MCAS.

  • Genetics
  • Gut Dysbiosis (severe gut flora imbalance in the gut microbiome)
  • Gut infections (SIBO, Candida, H Pylori)
  • Mould infection 
  • Lyme infection
  • Chronic stress
  • Toxins

If you discover that you have MCAS, you'll need to be diligent throughout your life. This means working hard to heal your gut and health issues that cause MCAS, heal infections, detox from metals and manage your nutrition and stress well.


I know it is a lot to take in and process. That is why we said it is very complex, as there are so many factors to consider and potentially address.


How to Test for MCAS

Testing for MCAS can be tricky as a mast cell mediator (such as histamine), may only be present during a MCAS flair-up.

Effective testing needs to be done right around the moment of the flair-up and tests should be conducted by an experienced practitioner.

Be aware, that neither a positive nor negative test is 100% accurate. You might test positive to that particular mediator at that time and not have MCAS or you may test negative to that mediator and have MCAS.

The main way to know is by your own symptoms. Keeping track of your triggers by making a note in a journal and chatting to the natural doctor.

If you do want to do the mediator tests, ask your practitioner to test for:

  1. Tryptase (less than 4 hours after a MCAS flair)
  2. Urinary N-Methylhistamine and prostaglandins D2, DM and F2a tests


Here are some guidance points to help summarise:

  • Work on healing the gut with a proper diet (I highly recommend an animal-based, low-fibre diet and healing foods you can find here.)
  • Heal your gut infections such as candida, SIBO, and H.Pylori.
  • Heal a leaky gut if that is a problem for you, as many issues arise from a leaky gut.
  • Detox from mould infection (if the mould in your home is nasty, you might have to relocate as I did)
  • Heal your Lyme infection (which can also often be a mould infection that's been diagnosed as Lyme)
  • Detox from heavy metal toxicity safely and whilst under the care of a trusted health practitioner 
  • Get a handle on your stress (if you have poor stress control due to Pyrrole disorder). Ensure you manage this with the correct Nutritionals and calming practices such as yin yoga, meditation, and time barefoot in nature.
  • Clean up all the toxins in your environment (your food, cleaning products, personal care etc.)


List Of Things to Consider Cleaning Up When You Have MCAS

  • Cleaning products (use baking soda, lemon juice, borax, essential oils and white vinegar for cleaning instead)
  • Air fragrances (use pure essential oils in a diffuser)
  • Garden pesticides/weed killer (use pine oil weed and pest remedies found online)
  • Personal care products (makeup, bath/shower products, perfumes, body sprays, deodorant (try our natural mineral deodorant), body lotions, tanning products, talcs, douches/feminine hygiene products, tampons, pads, liners, nail polish, haircare etc.
  • Laundry products (choose natural detergents, avoid fabric softeners, ironing starch, bleach and dryer sheets)
  • Cooking equipment: Avoid Teflon and aluminium and opt for a good quality ceramic fry pan and stainless steel pots and pans. Avoid iron if you have an iron overload (which many people have).
  • Storage containers: avoid BPA plastic containers and choose stainless steel containers or glass where possible
  • Choose certified organic produce where possible to avoid agricultural chemicals and GMOs.
  • Choose certified organic wine without preservatives (remember that wine is high in histamine too, which may cause HIT)
  • Use house plants to soak up toxins in the air (ficus, peace lily, philodendron, snake plant etc.)
  • Use an air purifier and clean the filter regularly.
  • Clean the filter in your car air conditioner
  • Diffuse essential oils in your car, home and office (check for pet-friendly ones if you have a pet nearby)
  • Open your windows and let the fresh air and natural light in
  • Get the early sunlight into your eyes and onto your skin to stimulate healing. 
  • Keep your house and environment clean with natural practices.


NOTE: nothing we say here is to be taken as health advice; we always encourage people to work closely with an integrative/functional/naturopathic doctor and get the proper testing.


How to Treat MCAS


Whilst you can't do much about your genetics, you can do lots with your epigenetics. We will discuss this topic later in the blog.


Firstly, you will need to determine whether you have this or not. Speak to a functional/integrative/naturopathic doctor for advice.


If you could find someone specialising in this area, that would be even better!


The list we are about to share is not to be interpreted as health advice, but their advice may look like this. Some of this we may be repeating, so just go with it.

  1. Eat a Low-histamine diet (see our blog series on HIT here)
  2. Use a DAO supplement (try this one from Return2Health). We aren't affiliated with this company in any way. I wish we could stock the Seeking Health brand, but I am not a practitioner).
  3. Use antihistamines if necessary. DAO supplements can only do so much; you may need to deal with the endogenous histamines (made in your body). You can do this with natural antihistamines and mast cell stabilisers (see our footer for recommendations). Try adding more natural antihistamine foods to your diet and mast cell stabilisers.
  4. Identify Toxins: We briefly spoke about mould, which is one of the worst! Please remove mould safely. If the mould is out of control, you may have to consider moving house. I know it sounds extreme, but your health is worth it. Mould infection is hazardous! I lived in black mould throughout 2021, which caused my health to suffer greatly.
  5. Get sweaty: use a sauna, exercise or take hot detox baths to get the sweat happening and the toxins out of you. Sweating is vital for removing toxins from the body and has been safely shown to remove arsenic, BPA, cadmium, lead, mercury and phthalates. 
  6. Get adequate sleep: When we lack proper sleep, this can upset the mast cells' "circadian clock"! This clock regulates the severity of allergies during the day. Also, when sleep is poor, these cells lose rhythmicity. Keep your mast cells in check by getting to bed before 10 pm and ensure you have a quality sleep. Read our sleep blog here.
  7. Get a Handle on Stress: One way to seriously burden your immune system is to be unconscious of your stress and allow it to be chronic. Suppose you have a condition that affects your stress control (such as pyrrole disorder). In that case, it's essential to manage this with correct supplementation and stress management practices. How you deal with life's challenges matters. The thing is that stress negatively impacts our gut microbes (allowing the bad ones to flourish), which can have a lousy flow on our body and health (including MCAS). Stress hormones can lead to the degranulation of mast cells. When this happens, proinflammatory mediators such as histamine are released. Stressors can also be chemical and environmental (not just emotional), so be mindful of what causes stress to your system.
  8. Work on your gut health: this chapter is too long to have in bullet point form, so I will continue below.


Working on Your Gut Health


Gut Microbiome

Looking after your gut health means taking care of your gut microbiome (restoring balance). Support your gut health with the proper diet for whatever your needs are. Everyone is individual and goes through different things.


I tried the carnivore diet, which helped my gut more than anything. I then realised I was getting too many histamines as I ate aged beef*, so now I only eat fresh meat. 


*I have HIT and possibly MCAS, just FYI. Aged beef is incredibly high in histamines. Seafood also can be, and I was eating much seafood as well.


If you can't access organic fresh meat at your local butcher or supermarket, try Our Cow. I contacted them about their meat, and they said it is not aged as it is turned over so frequently.


Restoring gut microbiome balance may also require adding an excellent prebiotic fibre such as organic baobab. Adding prebiotic fibre can help to feed the good gut bacteria/flora and allow them to flourish.


Eating less or no sugar is also a good idea. Sugar consumption feeds the harmful microbes, allowing them to proliferate.


Be mindful of foods that turn into sugar, such as grains and legumes.


Gut Infections


Work to heal your gut infections (under the care of a health practitioner). These infections are SIBO, candida, and H.Pylori.


Leaky Gut Syndrome


A leaky gut is problematic for health, so addressing this issue must also be mentioned. Work to heal the gut lining with diet and supplementation.


It makes me crazy when I see people putting spinach and kale in smoothies when there is so much information on how harmful this can be.


How is putting spinach or kale in your smoothie harmful? These things are high in oxalates and very hard on the digestive system even though they've been blended.


Oxalates can break down the gut lining (amongst many other adverse effects). 


Many plant foods are high in this plant toxin and should be limited if you want excellent gut health. Sorry, but it is just the truth.


Humans rarely possess the specific type of bacteria that break down oxalates (Oxalobacter formigenes). Because we don't have Oxalobacter formigenes, these oxalates stay in the system and cause many health issues.


Eat low-tox veggies and fruits to avoid problematic lectins (another plant toxin). Eating nuts, seeds and legumes is not recommended because they contain phytates (like oxalates) that can bind to crucial nutrients and be hazardous.


If you must eat these things, please at least prepare them properly by soaking, sprouting and activating where necessary. Choose certified organic as well to reduce harmful agricultural chemicals.


Take an Appropriate Probiotic


If you are taking a probiotic or considering one, ensure that it supports HIT and MCAS. I speak about this in my blog here.


Many people are unaware that the wrong probiotic can harm their healing journey because some (many) probiotics create histamine!


I learned this valuable lesson the hard way!


Eat a Diet that Focuses on Organic Produce


Eating organic should not be an elitist thing, and if you genuinely cannot afford to do so, I am sorry; I wish you could.


I'm a big believer in the importance of eating organic produce, as glyphosate is real. Glyphosate is undeniably harmful to the gut microbiome. 


When our diet includes more easy-to-digest animal protein and fats and fewer plant toxins and plant fibre, this can allow our gut to heal more effectively.


Natural Antihistamine Foods & Mast Cell Stabilising Foods


We discuss foods you might like to incorporate into your diet that have histamine healing benefits due to their nutrients.


Mast Cell Stabilisers

  • Khellin: (find online)
  • Quercetin: known to block the release of proinflammatory mediators. Acerola is a good source of natural quercetin.
  • Silibinin: This can help prevent histamine release and other proinflammatory agents released by mast cells. Milk Thistle is a good source of silibinin. The liver detox support contains milk thistle and other histamine helpers such as artichoke, turmeric and coriander.
  • Ellagic Acid: This may help to stop histamine and other proinflammatory agents released by mast cells. Perfect Resgrape contains ellagic acid.
  • Resveratrol: This compound has been found to suppress the inflammatory cytokines related to mast cell disorders (TNF and interleukins). Also available in ResGrape products.
  • Curcumin: This is a turmeric compound with known anti-allergic activity and the ability to stabilise mast cells. Also found in the Perfect Liver Detox Support supplement but the Turmeric Plus and Hab Shifa product.
  • Mangosteen: Shown to inhibit the release of histamine.
  • Theanine: This amino acid (found in green tea) may help to prevent histamine release. Be mindful of your consumption, as green tea contains a small amount of caffeine. Caffeine is a DAO-blocker. You can find theanine in the Perfect Matchinga powder (organic matcha and moringa). Moringa is also a rich source of quercetin.

Natural Antihistamine Foods

  • Thyme*
  • Parsley*
  • Coriander*
  • Basil*
  • Watercress
  • Broccoli*
  • Mung bean sprouts
  • Fennel*
  • Ginger*
  • Holy Basil/Tulsi*
  • Pomegranate

*Fresh and organic is best. 


You can find this information in our blog here.




Epigenetics can be described as Environmental factors that turn genes on and off. These factors determine how cells respond to particular genes—also known as 'gene expression'.


We have much control over this through our minds, our lifestyle and the choices we make.


Did you know that something as simple as getting enough B vitamins can protect us against pollution? Pollution can have adverse epigenetic effects.


Eat more liver (or take a liver supplement) and take Acerola for more B vitamins.


Consuming a low-carb, high-fat diet can also be helpful, but this gets into nutrigenomics. We will talk more about this soon.


Epigenetics also deserves an entire blog, which we will soon publish.



















Finn, D. F., and J. J. Walsh. “Twenty-first Century Mast Cell Stabilizers.” British Journal of Pharmacology Br J Pharmacol 170.1 (2013): 23-37. Web



Disclaimer: This article is strictly informational and not intended as health advice. Statements made have not been evaluated by the TGA and are not intended to treat, diagnose, cure or prevent. One should always consult with their trusted health professional before adding a new supplement to their diet.



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