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Do I have mast cell activation syndrome?

Find out if this little-known condition is behind your body-wide symptoms.



Researchers have known about mast cell activation syndrome for decades, but it’s only recently become a condition that can be identified and addressed in clinic.

What is mast cell activation syndrome?

Mast cell activation syndrome (MCAS) is a condition in which your mast cells release too many inflammatory substances too often [1].

Mast cells are special immune cells that hang out in all of your body’s tissues, but they particularly like to congregate where your body comes into contact with the environment—such as in your gut and on your skin.

Mast cells are constantly on alert for danger, so they carry around sacs of inflammatory substances. When you’re exposed to stress or a threat, they break open these sacs and release the pro-inflammatory substances to protect you.

This is easy to understand if you picture mast cells as soldiers with cannons. When they sense danger, they dip into their bags of gun powder and start firing the cannons.

This process—known as ‘mast cell degranulation’—is a normal bodily process and it’s useful in the right amounts. If you inhale something unpleasant, your mast cells will kick into action and make you sneeze to get rid of it.

But MCAS is when your mast cells release too many substances too frequently—or when the soldiers keep firing those cannons. This is subtly different from mastocytosis, a rare condition in which the body simply produces too many mast cells [2]. In MCAS, you have a normal number of mast cells, but they’re too active.

The substances produced by mast cells are called ‘mediators’. The most well-known mediator is histamine, but they also include tryptase, prostaglandins and leukotrienes [3]. If a person with suspected histamine intolerance doesn’t improve with a low-histamine protocol, it may be because they’re suffering from MCAS and the other mediators are still causing problems.

What are the symptoms of mast cell activation syndrome?

Your mast cells are found all over your body, which means they can create symptoms everywhere. The most noticeable symptoms tend to occur in the skin, gastrointestinal tract, nervous system and heart.

The symptoms also exist on a spectrum. Anaphylaxis is on the end of the scale, but milder symptoms can include [4]:

  • Itching and flushing
  • Hives
  • Watering eyes
  • Runny nose
  • Sneezing
  • Swollen tongue or lips
  • Shortness of breath
  • Wheezing
  • Low blood pressure
  • Rapid heart rate
  • Diarrhoea
  • Nausea
  • Abdominal cramps
  • Headaches
  • Fatigue

Brain fog is a tell-tale symptom too. This can leave you finding it difficult to concentrate, or even give you problems with your memory or word recall. Mood disorders—such as depression, irritability and anxiety—can appear as part as MCAS too.

Unlike an allergic response, these symptoms don’t appear in isolated attacks [5]. They tend to be chronic, which can become frustrating and even debilitating.

What causes mast cell activation syndrome?

There’s no one cause of mast cell activation syndrome. It’s the result of accumulated threats to your body.

We know that 74% of people with MCAS have one first-degree relative who also suffers from it, so there may be a genetic susceptibility [6]. We also know that people who are poor methylators are more prone to developing MCAS—likely because methylation is one of the body’s primary ways of getting rid of histamine [7].

MCAS has also been associated with obesity, IBS, depression and diabetes [8]. We don’t yet know if MCAS plays a role in the development of these conditions, or if it’s the other way around, but we do know they’re connected.

But even if you have a genetic susceptibility, a methylation issue or a pre-existing condition, something has to trigger MCAS. These triggers can include:

  • Insect bites
  • Food sensitivities
  • Antibiotics
  • Painkillers
  • Rapid temperature change
  • Pain
  • Chronic tiredness
  • Infection
  • Hormonal changes
  • Chemical exposure
  • Emotional distress

But that’s still not the whole story. A trigger can only light the fuse of a fully loaded canon—which means that to develop MCAS, your mast cells have to already be irritated by something.

But what could be stirring up your mast cells without you realising it?

There are three common culprits:

Heavy metals. Metals such as aluminium and mercury destabilise mast cells [9].

Gut dysbiosis. More than 70% of your immune system is clustered around you gut, which means an imbalance of bacteria can activate mast cells [10].

Mycotoxins. Chronic exposure to environmental pathogens activates mast cells. This one is huge. In our clinical experience, mould exposure or sick building syndrome is at the root of 90% of MCAS cases.

How you do you get a mast cell activation syndrome diagnosis?

MCAS is difficult to diagnose because the symptoms are both far-reaching and non-specific.

According to guidelines, you have to hit three criteria before you’re suspected to have MCAS [11]:

1) Your symptoms affect at least two body systems and they’re recurrent. There’s no other condition causing them.

2) Blood or urine tests performed during an episode show elevated levels of mediator markers.

3) Medications that block the effect of mast cell mediators give you relief from symptoms.

This is made even more complicated by the fact that there’s no single test used for point 2). Serum tryptase and whole-blood histamine can be used as markers, but so can urinary histamine metabolites such as N-methylhistamine [12].

You can also work with a Functional Medicine Practitioner who can make a clinical assessment.

What’s the best diet for mast cell activation syndrome?

A common approach to MCAS is to follow a low-histamine diet. This involves reducing or eliminating both foods that contain histamine and foods that stimulate histamine release.

Foods that are high in histamine include:

  • Fermented dairy: cheese, yoghurt, kefir
  • Fermented vegetables: kimchi, sauerkraut
  • Pickles
  • Kombucha
  • Cured meats
  • Alcohol: wine, beer, champagne
  • Vegetables: tomatoes, aubergine, spinach
  • Canned fish

Foods that are suspected to stimulate histamine release include:

  • Dairy
  • Seafood
  • Egg whites
  • Nuts
  • Cocoa
  • Some fruits: pineapple, bananas, oranges, limes, lemon, strawberries
  • Legumes

For some, this can bring great symptomatic relief. But it doesn’t work for everybody. This is because a low-histamine diet a) doesn’t entirely influence how much histamine your body makes b) doesn’t control how your body breaks down histamine and c) doesn’t tackle the other mediators that could be causing MCAS problems: tryptase, prostaglandins and leukotrienes.

For that reason, a standard anti-inflammatory diet that takes into account your sensitivities and intolerances is an alternative approach for MCAS. At its most basic level, this involves eating fresh, whole, nutrient-rich foods. Eating certain herbs and spices—such as peppermint, ginger, thyme and turmeric—can also help to stabilise mast cells [13].

What’s the best mast cell activation syndrome treatment?

MCAS is a complex condition and requires a multi-pronged approach.

Conventional treatment centres around stopping the effects of the mast cell mediators. Commonly prescribed medications include:

Anti-histamines. As the name suggests, these block the effect of histamines.

Mast cell stabilisers. These stop mast cells from releasing mediators (i.e. they stop the cannons from firing).

Antileukotrienes. These block the effect of leukotrienes, another type of mast cell mediator.

These can bring symptomatic relief, but they don’t address what’s causing the mast cells to overreact in the first place. That means that once you stop taking the medications, symptoms can return.

The natural approach aims to restore the normal function of the mast cells. This involves addressing several areas:

Diet. As discussed, a low-histamine or anti-inflammatory diet can help to reduce the mediator load.

Stress. Corticotropin hormone, released when you’re under stress, destabilises mast cells. This means a stress-reduction practice is an essential part of tackling MCAS [14].

Sleep. Research suggests your mast cells have a sleep-wake cycle too [15]. By supporting your circadian rhythm, you can help to bring them back into balance.

Supplements. Certain nutrients, are natural mast cell stabilisers [16].

These can all help to calm mast cells but, to achieve true resolution of MCAS, you also need to tackle the root cause of your mast cell aggravation.

By supporting your gut health, your immune system and your body’s detoxification processes, you can bring your mast cells back into balance. The process requires time and dedication and is best done with the support of a Functional Medicine Practitioner.

The effort is worth it. A comprehensive approach can put you in the driving seat once more, enabling you to get on top of MCAS—and your health as a whole.

Get in touch

Suspect you have mast cell activation syndrome or want to learn more? We have a wealth of experience across our practitioners in working with Mast Cell Activation Syndrome; helping people to manage their condition, and in some cases, to live a symptom-free life.

Suspect you have mast cell activation syndrome or want to learn more? Please feel free to get in touch to speak to one of our enquiry team.

Over the last 10 years, we have managed to turn many of our clients lives around by successfully treating numerous complex, chronic illnesses. We are a multi-disciplined health practice offering personalised nutritional medicine and naturopathy using the functional medicine approach. Some common conditions we support include; lyme disease, autoimmune disease, gut health, hormone health and unexplained illness. To understand what to expect when you attend the clinic and how successful our approach is, please have a read of our Google reviews and testimonials.

We offer a range of appointments in-person or online. Of course, with our virtual, online clinic, you’ll receive the same exceptional service from your practitioner as you would seeing us at our London clinic.

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