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mast cell activation syndromeMast Cell Activation Syndrome (MCAS), also known as Mast Cell Activation Disorder (MCAD), is a syndrome where the mast cells are overactive and produce too many chemical mediators. Unlike mastocytosis, where there are too many mast cells, in MCAS, there are normal numbers of mast cells, they are just misbehaving and producing too many inflammatory chemicals.

Mast cells are types of immune cells; they mediate inflammatory processes including hypersensitivity reactions and allergic reactions. They produce and release chemicals including histamine, interleukins and enzymes. Mast cells are found scattered throughout various tissues of the body – especially just underneath the skin (which is why hives are so common in allergic reactions), near blood vessels, in the respiratory, digestive and urinary tracts. This broad dispersion of mast cells is the reason why symptoms of MCAS can impact multiple systems of the body.

MCAS has characteristics of an allergic reaction, a chronic inflammatory response, and an autoimmune disorder. The symptoms often resemble allergies, but are typically chronic in nature, waxing and waning over time, often without clear triggers. In severe cases, anaphylaxis can occur, which can be life threatening.

Most common symptoms include wheezing, shortness of breath, coughing, chest tightness, heart palpitations, lightheadedness, hives, itchy skin and flushing; but can also include more broad symptoms such as chronic fatigue, brain fog and temperature regulation problems. Food sensitivities are common, along with digestive symptoms such as nausea, vomiting and diarrhea.  There is a connection between MCAS and POTS. There may also be a relationship between histamine response and mold toxicity. Click here to read an interesting interview about that connection.

The first step in treatment for MCAS is to adopt a low-histamine diet.  There are a number of different resources online for helping in this area.  I particularly like The Low Histamine Chef (aka Yasmina Ykelenstam).  Some sources are more liberal and some are most strict; some people will be able to be a little more free with their diet than others. Here’s a starting point though. You want to avoid high histamine foods, and foods that trigger the release of histamine.  You also want to avoid foods that block diamine oxidase, which is the main enzyme that metabolizes the histamines you may ingest. Choose foods that are on the low histamine list.

High Histamine Foods

  • Alcohol
  • Pickled or canned foods – sauerkrauts
  • Matured cheeses
  • Smoked meat products – salami, ham, sausages….
  • Shellfish
  • Beans and pulses – chickpeas, soy beans, peanuts
  • Nuts – walnuts, cashew nuts
  • Chocolates and other cocoa based products
  • Vinegar
  • Ready meals
  • Salty snacks, sweets with preservatives and artificial colorings

Low Histamine Foods 

  • Fresh meat (cooled, frozen or fresh)
  • Freshly caught fish
  • Chicken (skinned and fresh)
  • Egg yolk
  • Fresh fruits – with the exception of strawberries, most fresh fruits are considered to have a low histamine level (also see histamine liberators below)
  • Fresh vegetables – with the exception of tomatoes
  • Grains – rice noodles, yeast free rye bread, rice crisp bread, oats, puffed rice crackers, millet flour, pasta (spelt and corn based)
  • Fresh pasteurised milk and milk products
  • Milk substitutes – coconut milk, rice milk
  • Cream cheese, butter (without the histamine generating rancidity)
  • Most cooking oils
  • Most leafy herbs
  • Most non-citric fruit juices
  • Some Herbal teas

Foods That Trigger The Release of Histamine

  • Most citric fruits – kiwi, lemon, lime, pineapple, plums…
  • Cocoa and chocolate
  • Nuts
  • Papaya
  • Beans and pulses
  • Tomatoes
  • Wheat germ
  • Additives – benzoate, sulphites, nitrites, glutamate, food dyes

Diamine Oxidase (DAO) blockers:

  • Alcohol
  • Black tea
  • Energy drinks
  • Green tea
  • Mate tea

There are also some supplements that can help with MCAS.

Histamine Block – this is a source of the DAO enzyme that can help to metabolize histamines.

Activated Quercetin – this contains quercetin, bromelain and vitamin C, all known to be mast cell stabilizers.

Ther-Biotic Complete Probiotic – as with any immunological issue, especially one that can be triggered by foods and has digestive system involvement, a probiotic is important to promote a healthy gut biome and reduce inflammatory response.

MCAS is not well understood and is probably not adequately diagnosed, since many of the symptoms are quite vague and could be attributable to many other things.  I think the relationship between MCAS and mold toxicity is fascinating, and well worth further investigation.  I wrote about the severity of mold toxicity here are while back, so for anyone suffering from MCAS, looking into mold exposure would be a good idea.  I have also had a handful of patients with Lyme disease who also had MCAS.  I have never used Low Dose Naltrexone in my patients who have presented with MCAS but given it is immune modulating, anti-inflammatory and is frequently used to balance auto-immune processes, it would seem to be worth a therapeutic trial.

Anyone with MCAS would probably benefit from working with a nutritionist or dietician to help guide their diet, then I would add the above three supplements too.  I would expect to see improvement within a month using that two-tiered approach.