Find out more about this condition, and how to manage it by reading my page below.
This stands for Mast Cell Activation Syndrome. This means that the body produces high levels of inflammatory cytokines and histamine, in particular. This has become my own specialist area of interest, and I have studied widely around this topic, reading extensively and listening to lectures by some of the top experts working in this field today, in order to improve my own understanding. By understanding MCAS, the effects of histamine, and how to control it through diet and lifestyle, I have improved my own symptoms enormously, and I now work to support others by providing information to help them do the same.
What is MCAS?
Mast Cells are a part of the immune system, and they are located throughout the body. They are particularly found in mucous membranes throughout the body, including the mouth, the throat, the lungs, the digestive tract and bowel, the cardiovascular system and heart, the bladder and urinary tract, the eyes, the nose, and the skin. They also line the nervous system and are present in the brain, and interact closely with neurons, or nerve cells.
Mast Cell Activation Syndrome is a condition where the mast cells are over activated, overly sensitive, and react inappropriately to a whole multitude of triggers. When they react, it is called ‘degranulating’ and during this process they release up to 200 different chemical mediators, including cytokines, histamine, bradykinin, prostaglandins, and leukotrienes, amongst others. The majority of these substances act as pro-inflammatory mediators, meaning that they create inflammation in the body.
From this, you see how Mast Cell Activation can cause widespread, systemic symptoms anywhere in the body, depending on where the Mast Cells are degranulating and releasing their inflammatory chemicals, producing inflammation in that area.
Getting a diagnosis of MCAS can be tricky, as there are no reliable tests that can detect the mediators that mast cells release. Some practitioners test for histamine or prostaglandins, but these degrade very quickly and are very sensitive to heat, so the test must be stored correctly and kept cool, and processed in a specific way, which means that they are often unreliable. There are not many places in the UK currently where you can get these done. Because of the fact that they are very unreliable, many MCAS experts make a clinical diagnosis. A clinical diagnosis of MCAS is often made when
1. Other possible causes, such as IgE mediated allergy or other conditions, have been ruled out
2. Symptoms are present in 2 or more body systems. If symptoms are only digestive or only affect the skin, for example, it is not thought to be MCAS. Many people have symptoms in more than one body system, but for it to be considered MCAS, there must be symptoms in at least 2.
3. Trialing antihistamines and mast cell stabilising drugs improves symptoms. This is a tricky area, as it is also recognised by experts that people with MCAS can often react to the medications that are supposed to help them! So, this needs to be borne in mind when making a diagnosis.
Different specialists currently use different diagnostic criteria. Some test, others rely on clinical diagnosis based on symptoms.
The UK Charity Mast Cell Action UK has a list of specialists who are MCAS-aware, and they can provide this if you contact them via their website.
How Common Is MCAS?
According to some MCAS specialists, as many as one in 6 or one in 7 people may have underlying, undiagnosed MCAS, and they believe it is much more common in the general population than is currently realised. MCAS is also thought by some specialists to be possibly involved in some cases of ME/CFS, and I know that extreme fatigue is certainly a symptom for me. Because MCAS is tricky to diagnose and there is a lot of medical controversy about how to diagnose it, doctors are not routinely taught about it, and some doctors don’t believe that it exists. This means that it is rarely diagnosed, but not necessarily that it is rare!
Potential triggers for MCAS
Unlike in typical IgE mediated allergy, where the immune system reacts to specific, identified triggers and produces antibodies, in MCAS, the mast cells react without the production of antibodies, and it therefore cannot be identified through normal allergy tests. This is called idiopathic mast cell activation, or non-IgE mediated mast cell activation. In someone with MCAS, almost anything can be a potential trigger for mast cells to degranulate, and each person’s individual triggers will be different, and can vary over time, as their mast cells become sensitised to different things and more unstable. Identifying what your particular triggers are is the first step towards learning to live with MCAS and how to manage it successfully. The best way to do this is to keep a very detailed daily diary.
It is important to understand that it is not just food that triggers MCAS, so your diary must include all things that you have experienced in order to begin to see patterns in your symptoms, and possible causes. You should include toiletries you use, cleaning products, places you visit, rooms you spend time in, any products you use, fragrances or scented things you come into contact with, exposure to toxins such as cigarette or vape smoke, exposure to pesticides, exposure to plastics. VOCs, or Volatile Organic Compounds can be a big trigger for us. These are found in a wide variety of products, including aerosol sprays, paints, new furniture etc, and they can off-gas from new products for many months.
Brain fog, memory loss, poor concentration, headache, migraine, 'buzzing' sensations, numbness, tingling, weakness, nerve pain, insomnia, anxiety, depression, agitation.
Coughing, shortness of breath, 'air hunger' (when you feel as though you can't take a full breath), post-nasal drip, catarrh, sinus pain, wheezing, asthma.
Flushing, rashes, dermatographia (marks on the skin after light scratching), hives, burning, itching, rosacea, eczema, psoriasis, burning, slow wound-healing, bruising.
Diarrhoea, constipation, bloating, flatulence, abdominal pain and discomfort, nausea, vomiting, indigestion, reflux, IBS, allergies and food intolerances, burning mouth, gum issues, weight issues (under and overweight), SIBO
Tachycardia (fast heartbeat), bradycardia (slow heartbeat), palpitations, high blood pressure, low blood pressure, dizziness, changing or unstable heart rate or blood pressure, chest pains, fainting.
Bladder inflammation and pain, burning or pain on urination, symptoms of UTI or cystitis, urinary frequency and/or urgency, endometriosis, painful periods, hormonal imbalances, fertility issues, vulval pain and itching.
Hyperflexibility and hypermobility, joint pain and joint inflammation, muscle pain, muscle spasms, cramps and involuntary muscle twitches, osteoporosis, osteopenia, spinal disc degeneration.
Swollen glands and swollen lymph nodes, sluggish lymphatic drainage, weight gain and swelling, spleen pain and spleen enlargement.
Hearing and visual disturbances, blurred vision, tinnitus, sensory sensitivity, watering eyes, itchy eyes, red eyes, burning and sore eyes, crusty eyes and ears.
It is important to understand that people who have MCAS may experience anaphylactic episodes and these can be life-threatening, just like any other anaphylaxis. The symptoms of anaphylaxis include difficulty breathing and throat swelling, itching, hives, swelling lips, flushing or pale skin, rapid and weak pulse, nausea, vomiting, feelings of doom, diarrhoea, dizziness, fainting, loss of consciousness. If you or a loved-one experience a combination of any of the above during a reaction, it is essential to seek urgent medical advice from 111 or A&E
This can be any foods and drinks, not just foods which are traditionally considered to be allergens. People with MCAS often react to many foods, and some people have very limited diets. Foods that are high in histamine are particularly difficult, and people often have to strictly follow a low-histamine diet. Good advice about low histamine diets can be found in the web links at the bottom of this page. Gluten, diary and eggs are often problematic too.
Medications and particularly the fillers, dyes and excipients that are found in medications can be problematic. It is ironic that people with MCAS often react badly to medications that should be helpful, such as antihistamines, and this is not unusual. Finding the right medications that work for us can be challenging and requires an understanding medical professional who is willing to try different options. Some people find they can’t tolerate any medications, and rely on natural mast-cell stabilisers and antihistamines.
It can seem unfair, and counter-intuitive, but many common herbal remedies and even supplements can trigger reactions. I have also had reactions to homeopathic remedies. Many people struggle to tolerate supplements like Vitamin C, Vitamin B12, Evening Primrose Oil, etc. Herbs and supplements can be very helpful for supporting MCAS, and there are some very useful antihistamine and mast-cell stabilising herbs and supplements, but always introduce one thing at a time and start with very tiny amounts to ensure you are not reacting to it before you continue. Some supplements contain fillers, dyes and other ingredients that can be the problem, so always find the purest supplements you can. Vitamin C, for example, is often problematic because supplement forms are often by made by fermenting corn, which is a trigger for many. You may need to experiment to find a format of supplement that works for you.
Temperature changes can trigger mast cells. Extreme heat can be a trigger for some, for others it is cold, and for others it is changes in temperature that trigger their mast cells.
As explained above, chemicals like fragrances, room scents, washing powders, paints, plastics, glues, cleaning products, VOCs, etc, can all be triggers for people with MCAS. Some people suffer very badly with chemical exposure and become very reactive to them, others are not affected by chemicals, and have other triggers instead. It is different for everyone, each person will have their own things that trigger their reactions, depending on what their immune system is objecting to. Working out what chemicals are bothering you and avoiding products with these in is a key part of stabilising.
Similarly to the chemicals listed above, personal care products such as deodorants, shower gels, shampoo, conditioner, makeup, hair products, etc all contain chemicals and fragrances, and these can prove to be very problematic. Finding alternatives that have a few natural ingredients can be really helpful in stabilising mast cells.
Mast cells and neurons, or nerve cells, are very closely linked, and they communicate with each other. So, when we feel stressed, worried, anxious, emotional or overwhelmed, our nervous system communicates ‘danger’ to our mast cells, and they respond. So, working on our mental health and avoiding stress is a key part of managing MCAS. It is important to try and stay calm when you are reacting, even though it is difficult when you feel so poorly, and only natural to feel upset. However, getting upset could well just trigger your mast cells even more, so it can be helpful to develop your own 'chill out routine' to implement when you need it. Relaxation techniques such as meditation, mindfulness, self-hypnosis, or herbs (if tolerated) that can help keep us calm and relaxed can be useful.
Having said that, it is also important to understand that the mediators released by Mast Cells also affect the nervous system, so feeling ‘anxious’, ‘wired’ or depressed can also be a symptom of a reaction, and can be caused by the chemicals released by mast cells causing inflammation in the nervous system. So, it is important to recognise that this is a symptom, and not blame yourself or beat yourself up for 'feeling anxious'. MCAS can affect our mood, and it’s important for you, and for loved-ones, to understand this.
This category also includes anything that puts the body under stress. We think of stress as mental or emotional stress, but exercise and demanding physical activity, lack of food or deficiency in a particular nutrient, dehydration, lack of oxygen, sickness like colds and flu, and any parasite or viral or bacterial infections, all put the body under stress and can trigger MCAS reactions.
It is not yet known what causes MCAS. Some people are born with it, and some develop it over time. There is some evidence that it may run in families, as often more than one generation is affected, so some people think there may be a genetic component. More research is needed to understand it fully.
Some practitioners believe that environmental factors are involved in causing MCAS. For example, imbalance in the gut flora, known as dysbiosis, can cause the gut lining to become permeable, and allow things that shouldn’t be there into the blood steam. Mast cells line the gut and are directly affected by anything passing through the gut lining, so they can become over stimulated when this happens, leading to systemic mast cell upregulation.
For some, an overload of toxins and ‘stressors’ on our immune system can overburden it and cause it to become over-reactive. This can happen from chronic exposure to every-day environmental toxins, exposure to mould, and exposure to viral and bacterial infections. Bacterial infections release toxins into the body constantly, and so there is a constant toxin exposure happening. Either a one-off exposure to a large amount of a toxic substance, or a long-term, chronic exposure to products containing small amounts of toxins can trigger the mast cells to become over-active.
Viral, bacterial or parasite infections can be a big underlying 'driver' for MCAS to develop, as they put a continuous burden on the immune system, and 'provoke' the mast cells. This has also happened to some people following infection with Covid-19, and there is currently a lot of research happening into whether MCAS is a factor for those suffering from Long-Covid.
Many people with MCAS also have Dysautonomia and/or Ehlers Danlos Syndrome (EDS) or another hypermobility spectrum disorder, and these 3 conditions are often ‘comorbid’, meaning people often have them together. There is a lot of overlap with other conditions, such as ME/CFS, Fibromyalgia, Autism, interstitial cystitis, IBD, and autoimmune disorders such as Rheumatoid Arthritis, MS, Lupus, Hashimoto's Thyroiditis etc.
In my own personal case, I can now see that I have always had MCAS mildly, being sensitive to lots of foods and chemicals from birth, and I have always struggled with ‘allergy’ type symptoms, gut issues, bladder issues, skin issues, and musculoskeletal issues, but these were never connected, and treated in isolation. Other family members also had similar sensitivities. After contracting Glandular Fever, or Epstein Bar Virus, at 16, my allergies got much worse, and I suffered with undiagnosed Chronic Fatigue since then. I just thought I was ‘sensitive’ and ‘tired all the time!’ I have also had a lot of exposure to mould in my life, through places that I lived and from exposure at work, and I now understand that mould is a very involved in MCAS, because of the effect it has on the way the immune system functions.
The Connection with Lyme Disease
For me, it was when I contracted Lyme Disease in 2018 that my MCAS really went into overdrive, and I became very, very sick and began reacting severely to most foods, chemicals and virtually everything, overnight. My symptoms became really debilitating and took over my life, but because my most pressing symptoms were neurological and cardiac, it didn’t occur to me initially that they were an immune issue, and I didn’t initially connect them with the other systemic issues I was experiencing. So, it took me 8 months before I released that it was MCAS and that it was histamine that was my primary problem. Once I took control of my histamine levels through appropriate medications and diet and lifestyle changes, my symptoms really improved, but I couldn’t properly stabilise until I was diagnosed with Lyme and began treating for that.
I have since discovered that this is quite a common experience within the Lyme Disease community, and that many with Lyme develop MCAS. Dr Tania Dempsey, a Lyme Disease and MCAS specialist in the US says that around 50% of her MCAS patients have Lyme Disease as the primary underlying driver. More research is being done in this area, and more is needed before Drs fully understand the mechanisms of how this works, and at the moment it is best to seek treatment to manage MCAS symptoms, and address Lyme Disease separately, if you believe that this may be an issue for you.
MCAS is a medically controversial area, and not well recognised within the UK yet. It can be difficult to find a specialist who is MCAS aware, and it is important to do your research to find the correct specialist. The Charity Mast Cell Action UK is the best source of information about Mast Cell Activation Syndrome in the UK, and they hold a list of specialists who are knowledgeable about MCAS. They can be contacted via their website https://www.mastcellaction.org/
An Alternative Option
Functional Nutritionists and Functional Doctors are often also knowledgeable on this subject, particularly how to manage histamine levels through diet, and how to identify your potential environmental triggers, and can often offer guidance to support people to find what their underlying drivers for MCAS might be and address these.
Always work with a qualified medical professional to get the right diagnosis and treatment for you.
These are a list of resources that I, personally, have found helpful in my own MCAS journey. I am not linked with or affiliated to any of these organisations, and I cannot take responsibility for external content.
Mast Cells United - Amber Walker
Toxic - Dr Neil Nathan
Never Bet Against Occam - Dr Lawrence Afrin
Mast Cell Activation Syndrome is a serious medical condition, and you should always seek professional medical advice if you suspect that you or a loved-one may have MCAS. All of the information presented on this website is based on my own personal lived experience of MCAS. I am not medically qualified and I do not claim to be able to cure or treat any medical condition. MCAS is a medically controversial area, and the information on this website should not be considered to be medical advice. The information contained in this website is for educational purposes only and I can't accept any liability for its accuracy. You should seek out qualified medical professionals to support you with any health diagnoses and conduct your own research.
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