Mast Cell Activation Syndrome

Here at My Pet Nutritionist, we deal with a huge amount of dogs with a variety of allergy symptoms. Some of our clients dogs have been diagnosed with Mast Cell Activation Syndrome (MCAS), which is an incurable disease, presented as repeated anaphylactic symptoms.

What are Mast Cells?

Found in the epithelial and mucosal tissues throughout the body, Mast Cells help regulate the formation of new blood cells, eliminate bacteria and parasites, and vasodilation as well as bone growth, and mineral homeostasis.

Mast Cells also regulate cell function in various cell types, including:

  • Dendritic cells
  • Macrophages
  • T Cells
  • B Cells
  • Fibroblasts
  • Eosinophils
  • Endothelial Cells
  • Epithelial Cells

While they’re very important parts of the body’s tissues, Mast Cells do produce and release substances which can be harmful in large quantities, including:

  • Histamine
  • Leukotrienes
  • Heparin
  • Proteases
  • Prostanoids
  • Cytokines
  • Chemokines
  • Growth factors

What Does Mast Cell Activation Syndrome look like?

There are a variety of symptoms associated with MCAS, including:

  • Swelling of the body, either localised to one area, or general swelling.
  • Nausea and vomiting
  • Acute diarrhoea
  • Hives
  • Reduced/low blood pressure
  • Difficulty breathing
  • Difficulty swallowing
  • Inability to stand or walk properly (may seem ‘drunk’)

If any of these symptoms shows, it is imperative to seek veterinary attention immediately. If these symptoms occur regularly, then your dog may need to undergo tests for Mast Cell Activation Syndrome.

What Causes Mast Cell Activation Syndrome?

It is unclear what causes MCAS to develop. It is often an idiopathic condition – meaning it happens without clinical reason.

As it’s a condition related to allergies, it’s important to discover, and eliminate the allergens from the diet, to reduce the risk of triggers for the pet.

One study suggests a possible link to the onset of MCAS, in patients with underlying immune disorders.

Findings Here

How Does the Vet Test for Mast Cell Activation Syndrome?

Blood tests will be carried out on your pet, to check for any elevated levels of histamines (which are released in the presence of a foreign body), tryptase (the markers of degeneration of mast cells, often produced during anaphylaxis), and prostaglandins (fatty compounds with a hormone-like effect in animals, which regulated inflammation).

If one, or all of these are present in abnormally elevated amounts, a diagnosis of MCAS may be given, particularly if these episodes are regular, and any prescribed antihistamines calm symptoms down.

Findings Here

The veterinarian may prescribe histamine 1 and 2 blockers, mast cell inhibitors, mast cell stabilisers, NSAIDs, immune suppressants, or other pharmaceuticals, which inhibit the production of histmaines and tyrosine.

One note to remember; some pharmaceuticals block DAO (Diamine Oxidase), which is the enzyme which breaks histamine down. We need histamine removed from the body as soon as possible so this is something to discuss with your veterinarian.

How Can we Support the Body?


At My Pet Nutritionist, we are all about feeding a fresh diet, whether it be raw, or lightly cooked. Your chosen diet MUST be low histamine. Avoid fermented foods like kefir, sauerkraut, and ACV as these are high histamine, and avoid high histamine plant matter such as spinach, pumpkin, strawberry, and avocado. If making bone broth for your dog, replace the ACV with lemon juice for a lower histamine option!

Read more about Mast Cell conditions, and low histamine diets here!

So, why is fresh food best for those diagnosed with MCAS?
  • Fresh food doesn’t contain unnecessary bulking ingredients, such as rice, maize/corn, other grains, legumes or nightshades. These ingredients all cause gut damage and/or are biologically inappropriate, and can be a major histamine release trigger.
  • Fresh food is minimally processed. Ultra processed ‘dog food’ is often contaminated with glyphosate, and Advanced Glycation End-Products (AGEs), which are both damaging to the gut.
  • It’s much easier to work on allergies and intolerances, using fresh food. This is important as we need to keep intolerances under control.

Keep the Gut Healthy

As with all potential allergy related issues, we need to keep the gut healthy! The gut microbiome is incredibly important to keep immunity strong, and reduce the risk of foreign particles being detected in the blood stream, having leaked from a gut with poor integrity. Any leaked particles will be targeted by histamine responses, which will increase the risk of a MCAS flare up.

Some gut health supplements include slippery elm, marshmallow root, Deglycyrrhizinated Liquorice Root. These should be paired with a good probiotic. The My Pet Nutritionist Gut Guardian supplement is perfect for dogs requiring gut work!

Work on allergies

Ensuring any potential allergies or intolerances are under control is essential! Those suffering with any Mast Cell related conditions must have their histamine levels under control at all times, to reduce the risk of a flare up.

As MCAS is heavily related to anaphylaxis, it is absolutely paramount that allergens are completely eradicated from the dog’s diet, and lifestyle.

In order to eradicate the allergens, an elimination diet is to be carried out, whereby one single protein is fed for numerous weeks, and is eliminated from the diet if the dog continues to worsen. Once some safe proteins are established, it’s important to stick to feeding only these proteins.

Read more on elimination diets here.


As well as the aforementioned gut healing supplements, there are a number of other supplements which may help support the body.

CBD: mast cells have cannabinoid receptors (like most cells in the mammalian body), which when inhibited, causes their production to be downregulated.

Findings Here
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Quercetin: found in various fruits, green vegetables and stinging nettles, quercetin is a natural antihistamine as it downregulates the enzyme responsible for converting histidine to histamine. Quercetin also reduces production of prostaglandins and histamines as it inhibits the cells responsible for their release. The inflammatory cytokines which cause inflammation as a large part of MCAS, are also inhibited, which decreases their production.

Findings Here
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Curcumin: this is the active component of turmeric; the main anti-inflammatory part. Another fantastic benefit of curcumin is that it inhibits mast cell degranulation.

Findings Here
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Green Tea: an easy, simple to get hold of supplement, green tea is incredibly high in polyphenols. It helps reduce degranulation of mast cells, and also inhibits inflammatory cytokine production.

Findings Here
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Silymarin: this is extracted from Milk Thistle (which is great to detox the liver), and helps reduce reactions caused by an MCAS flare up.
Findings Here
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Vitamin C: there are studies to suggest that a high vitamin C intake, equates to a low histamine output. A lot of quercetin supplements contain added Vitamin C!

Findings Here

  Does your dog have these symptoms, or have they been diagnosed by the vet? If you feel you may benefit from our help, don’t hesitate to book a consultation with one of our team!

Team MPN x

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