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Managing Mast Cell Activation Syndrome or Disorders (MCAS)  

Mast Cell Activation Syndrome (MCAS) is a type of Mast Cell Activation Disorder where the "chemicals called mast cell mediators are released too frequently or abundantly, and/or in response to triggers that are not typically considered to be harmful, for example; foods or chemicals in the environment. This can lead to which causes a wide range of symptoms that affect multiple parts of the body. MCAS forms part of a spectrum of mast cell disorders. People with MCAS may also have other mast cell disorders such as mastocytosis or hereditary alpha tryptasemia syndrome (HATS). Triggers and symptoms of MCAS vary greatly between individuals." (Mast Cell Action Website) Below you can find some examples of possible triggers.

Possible Triggers for MCAS Symptoms

Scents and smells:

  • Perfume and beauty products

  • Laundry detergents on peoples’ clothes

  • Scented cleaning products

  • Cooking smoke or BBQs

  • Tobacco or vape

  • Petrol or diesel fumes

  • Scented soaps and body washes

  • Synthetic materials e.g. car smells or furniture etc

  • Air fresheners 

  • Candles

  • Paint

Skin contact:

  • Vibration

  • Fabrics on our skin 

  • Insect bites

  • Animal fur or dander


  • Mould

  • Infections

  • Animal fur or dander

  • Pollen

  • Dust 

  • Scents and smells

  • Changes in climate

  • Changes in barometric pressure

  • Changes in temperature

Bodily activity:

  • Changes in body temperature 

  • Exercise 

  • Stress 

  • Anxiety

  • Hormonal changes


  • Medications

  • Foods (known trigger &/or random)

  • Liquids, even water

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What are MCAS Symptoms?

These can vary hugely between individuals. They can affect a whole range of body systems. MCAS is a condition that can fluctuate in severity over the course of someone's life and symptoms can vary over phases or come and go. It may be well managed at points, but less well managed at other points. Some triggers may be clearly identified but it can also be totally random or without a seemingly evident trigger. This PDF by Mast Cell Action charity outlines the symptoms, you can find them below too. 

Neurologic (brain and nerves)

Brain fog (memory and concentration problems )
Numbness, pain, or tingling skin Anxiety
Behavioural issues, rages

Nasal-ocular (nose and eyes)

Nose congestion
Eye watering and itching

Respiratory (lungs and breathing)

Sore throat



Shortness of breath

Throat swelling


Chest pain
Low blood pressure
Fast heart rate
Fainting or light-headedness


Joint and muscle pain

Osteoporosis (brittle bones)

Loss of bone mass



Stomach cramps or pain Reflux
Feeling or being sick Diarrhoea
Dumping syndrome
Food allergies or intolerance

Genital and urinary

Genital pain or swelling
Pain when urinating
Vaginal pain, discharge or itching

Bladder urgency or loss of control

Dermatologic (skin)

Itching with or without a rash

Hives or wheals


Extreme tiredness
Anaphylaxis, which can be life threatening

The Histamine Bucket Theory to Explain how MCAS may work

You can imagine your body with a histamine bucket that’s empty, but exposure to all things in the environment can gradually fill up the bucket to your personal histamine levels.


You may completely tolerate these things on some days, as your histamine bucket doesn’t fill up to the limit as quickly.


On other days it may overflow beyond the limits that your body can process the exposure to triggers and you’ll likely have more reactions and symptoms; to anything and everything.


A combination of managing triggers, reducing exposure to known triggers, and taking medication could all help to manage the level of your bucket.

Diagnosing MCAS

This can often be tricky as many healthcare systems still are not acknowledging the condition because only a handful of years ago the diagnostic criteria was established, and only around 15 years ago was the condition 'coined'. In the UK there are currently no NHS or NICE guidelines for the condition, which makes diagnosis difficult. Not all practitioners recognise or are aware of the condition. In addition, the methods for diagnosis aren't always accurate. There are thousands of mast cell mediators, yet we can only test ten and most healthcare systems only test one, so it's not surprising how challenging it actually is to diagnose 'objectively' and most diagnoses may be due to a positive response to medications and fitting the medical symptomatic profile.

If you're in the UK, you can find more information at Mast Cell Action. If you need support, the best thing to do is to contact the charity directly with info on your case and they'll be able to guide you with next steps. It's also important for them to gather data showing the need to governmental bodies, so if you need help please reach out to them directly here.

If you're in the US, you can find more information at TMS for a Cure

Managing Mast Cell Activation Syndrome

It's important to note that all information shared is for informational and not prescriptive purposes, and you should always consult a doctor to guide you further with this. 

Medications and Supplements

Mast Cell Stabilisers 

  • Ketotifen

  • Sodium Cromoglycate

Mediator Blockers 

  • H1 antihistamines 

  • H2 antihistamines

  • Anti-leukotrines

  • Anti-Prostaglandins


  • Prednisolone

Vitamins and Supplements

  • Vitamin C

  • Vitamin D

  • Probiotics

  • Magnesium

  • Quercetin

  • Luteolin

  • Sodium Butyrate

  • Liposomal L-Glutathione

  • Digestive Enzymes

  • Binders e.g. Toxaprevent

Antibody Therapies

  • Omalizumab (Xolair) 

Emergency Relief

  • Adrenaline Auto Injector e.g. Jext Pen or Epi-Pen

  • Albuterol reliever for asthma

Binders (to flush out histamine)

  • Toxaprevent - Histamine Protocol (KATYA5 for 5% off, affiliate link)

    • More info on this binder and how it helps me here

Other Strategies to Limit MCAS Triggers and Reactions


  • Following a low histamine diet.

    • This may reduce your bucket but you may also have triggers that aren't low histamine, so avoiding all trigger foods where possible too.

    • Keeping a food diary to establish triggers and symptoms from certain foods.

    • Look into other triggers beyond histamine like oxalates, salicylates etc.

    • Working with a dietitian or nutritionist to ensure that any restrictive diets aren't detrimental to your health.

  • Increases in blood sugar can trigger histamine release, so eating low sugar or refined sugar free foods where possible 

  • For low histamine and refined sugar free recipes, head over to My Accessible Kitchen, with recipes I develop to suit many elimination diets.

  • Looking at all labels carefully and advocating when eating out about dietary restrictions. You can create your own Allergy Cards and Foods That You Can Eat cards with my free templates on this page.


  • Using unscented beauty and hygiene products 

    • Asking people you live with to do the same

  • Patch testing everything before use

    • This may include getting sample sizes of products or finding brands that offer refunds if the products don’t work for you

  • Swapping to more natural alternatives and unscented versions of household cleaning products

  • Opting for dried flowers rather than fresh ones for home decor if pollen is an issue


  • Ensure you have all regular medications alongside abortive medications like asthma inhalers, EPIPEN and antihistamines when going out in public.

  • Asking people to kindly avoid spraying perfume or fragrance before you meet up with them or they come to your home.

  • Avoiding giving hugs to greet people. Even if they're not wearing perfume, their laundry detergent, shampoo or beauty products may have scents that could trigger you.

    • Before they approach you explain "I'm not doing hugs - air hug / fist bump / hand shake" if they ask why explain you have allergies and sensitive to scents. This may take some getting used to but I've found it's highly worth it.

  • Keeping away from places with tobacco smoke, vapes, wood burners, BBQs or simply staying out of the kitchen when food is being charred.

  • Showering (including hair wash) as soon as you're home from any outside location.

  • If people have pets that trigger reactions, even dander on their clothes can cause reactions so asking them to wear fresh out the wash clothes their pet hasn’t been on could help.

  • When you have guests over or are staying overnight elsewhere, using an air purifier with a HEPA filter to prevent reactions from additional triggers (like their beauty and hygiene products and laundry detergent etc). You can even bring a small and portable air purifier (that looks a little like a lantern) with you for travel.

  • Opting for socialising outside in open spaces if you are able to; at home or an another outdoor space.

  • Wearing a mask with an adequate filter to reduce exposure to airborne allergens, VOC's and fragrances.

  • Full rest and home isolation before and after exposure to triggers.

    • For me I aim to do this for many days to weeks depending on how my 'histamine bucket' is.


  • Opting for super soft bed linen to avoid reactions from rough fabrics. Always wearing clothes that are breathable cotton or soft fabrics that you tolerate. If you want to wear a knitted jumper in winter, wear a soft cotton basic top underneath to avoid rashes from fabrics.

Useful Resources

I'm constantly learning about MCAS and things I can do to manage debilitating symptoms and what can be done to change the system to enable better support in the future for others with MCAS. I'll share resources I've found helpful along the way for when researching on your journey with MCAS.


Mast Cell Action

TMS for a Cure


Dr Tania Dempsey and Dr Lawrence Afrin

Ehlers Danlos Society 

American Academy of Asthma and Immunology



  • Resources on their website about associated conditions to PoTS (MCAS)

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