Personalised Support for Mast Cell Activation Syndrome
(MCAS)

MCAS . HISTAMINE INTOLERANCE

At the Autoimmune Clinic, we specialise in mast cell activation syndrome (MCAS) and histamine intolerance, through a functional medicine approach.

WE GO BEYOND SYMPTOM MANAGEMENT TO UNCOVER AND ADDRESS THE ROOT CAUSE OF YOUR CONDITION, HELPING YOU REGAIN CONTROL OVER YOUR HEALTH AND WELLBEING.

At the Autoimmune Clinic, we specialise in supporting individuals suffering with MCAS and histamine intolerance through a functional medicine approach. We go beyond symptom management to uncover and address the root causes of your condition, helping you regain control over your health and wellbeing.

Living with MCAS and histamine intolerance can feel overwhelming, and the unpredictability of symptoms can make life very difficult. That's why our tailored programmes are designed to meet your unique needs, empowering you to take positive steps towards lasting health improvements.

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What is Mast Cell Activation Syndrome (MCAS)?

These symptoms can affect multiple organ systems and range from mild to severe, often resembling allergic reactions like skin rashes, digestive issues, breathing difficulties, and even anaphylaxis.

UNLIKE TYPICAL ALLERGIES, MCAS CAN BE TRIGGERED BY MANY DIFFERENT FACTORS, INCLUDING CERTAIN FOODS, ENVIRONMENTAL ALLERGENS, STRESS, AND PHYSICAL ACTIVITY.

The main challenge in treating Mast Cell Activation Syndrome (MCAS) is the mast cells' heightened sensitivity, which causes them to release excessive amounts of chemical mediators, either spontaneously or in response to harmless triggers. This overactivity can result in widespread inflammation and allergy-like symptoms that vary greatly in severity and presentation. For instance, an excess release of histamine may cause skin rashes, gastrointestinal issues such as abdominal pain and diarrhoea, neurological problems like headaches, and even cardiovascular instability. The diverse nature of these symptoms makes diagnosing and managing MCAS particularly difficult.

Mast Cell Activation Syndrome (MCAS) is a chronic immune system disorder where mast cells release an excessive amount of chemical mediators, such as histamine and cytokines, leading to a wide variety of symptoms.

WHAT ARE MAST CELLS?

Mast cells are a crucial component of the immune system, serving a key role in the body's defence. Distributed throughout the body, particularly in areas exposed to the external environment such as the skin, lungs, and digestive tract, mast cells act as first responders. Their main function is to detect foreign invaders or injury, triggering an inflammatory response that helps protect and heal the body.

"When your body always overreacts, think MCAS"

When mast cells encounter allergens, they release substances like histamine, which increases blood flow and vessel permeability, allowing immune cells to target the affected area. While this response is vital for fighting infections, it also causes common allergic symptoms such as itching, swelling, and redness. This dual role of mast cells—promoting healing and triggering hypersensitivity—shows their importance in health and the complications that arise when they malfunction.

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What are the symptoms of Mast Cell Activation Syndrome (MCAS) ?

BECAUSE MCAS AFFECTS MULTIPLE SYSTEMS IN THE BODY, ITS SYMPTOMS OFTEN MIMIC OTHER CONDITIONS, WHICH CAN MAKE THE DIAGNOSIS MORE DIFFICULT.

MCAS symptoms are highly varied, mirroring the broad distribution of mast cells throughout the body and the many different triggers that can activate them.

Individuals with MCAS may experience skin issues such as hives, redness, and itching, while also dealing with gastrointestinal problems like nausea, abdominal discomfort, and diarrhoea.

Respiratory symptoms, such as wheezing or difficulty breathing, are also common, and cardiovascular issues can include palpitations or fluctuating blood pressure and heart rate. Neurological symptoms may present as headaches, cognitive challenges, or mood disturbances.

Theirs bodies are damaged and they are left with a wide range of health conditions, some life threatening.

What about the remaining 75% of the population you ask? These individuals' immune system, when exposed to mould toxins, respond by binding with the invading poison that allows its cells to filter the biotoxins through the liver, kidneys, and other organs. No ongoing symptoms persist and the inflammatory process returns to normal.

MCAS Symptoms

BY ORGAN SYSTEMS

SKIN: Flushing, hives, angioedema (skin swelling), itching, skin rashes, dermatographism (red welts from scratching), chronic itching, urticarial pigmentosa (hive-like spots), easy bruising, reddish or pale complexion, cherry angiomas (skin growths), patchy red rashes, red face in the morning, slow-healing cuts, fungal infections, and lichen planus.

RESPIRATORY: Asthma, wheezing, shortness of breath, air hunger, dry cough, chronic obstructive pulmonary disease (COPD), difficulty breathing deeply, and chronic interstitial fibrosis.

GASTROINTESTINAL TRACT: Abdominal pain (especially in the left upper abdomen), splenomegaly (enlarged spleen), epigastric tenderness, nausea, vomiting, diarrhea, constipation, bloating, abdominal cramping, GERD/acid reflux, non-cardiac chest pain, cyclic vomiting syndrome, colonic and gastric polyps, and malabsorption.

EYES: Red, irritated, dry eyes; burning sensation; difficulty focusing vision; and conjunctivitis (pink eye).

words.

NOSE: Nasal congestion, sinusitis, postnasal drip, hoarseness, laryngitis, nosebleeds, and intranasal sores.

THROAT: Throat swelling, mouth or tongue sores, itchy throat, burning mouth, and difficulty swallowing.

EARS: Tinnitus (ringing in ears) and Eustachian tube dysfunction (blocked or popping ears).

NEUROLOGICAL: Numbness and tingling (especially in the hands and feet), headaches, migraines, tremors, tics, seizures (pseudo or true), brain fog (waxing and waning), memory loss, poor concentration, difficulty finding

CARDIOVASCULAR: Fainting, dizziness, lightheadedness, increased pulse rate (tachycardia), palpitations, hot flashes, postural orthostatic hypotension syndrome (POTS), blood pressure spikes or drops, fainting when standing, high pulse or temperature.

MUSCULOSKELETAL: Muscle pain, fibromyalgia, joint pain, osteopenia, osteoporosis, and weakness.

GENITOURINARY: Interstitial cystitis, recurrent bladder infections, sterile bladder infections, and frequent urination.

HORMONAL: Low libido, painful or heavy periods, infertility, and reduced sperm counts.

PSYCHIATRIC: Anxiety, depression, panic, obsessive-compulsive disorder (OCD), attention deficit/hyperactivity disorder (ADHD), short attention span, forgetfulness, and insomnia.

ANAPHYLAXIS: Breathing difficulties, hives, flushing or pale skin, warmth after exposure, weak or rapid pulse, nausea, vomiting, diarrhoea, dizziness, and fainting.

Triggers of MCAS

INDIVIDUALS WITH MCAS OFTEN EXPERIENCE SYMPTOMS TRIGGERED BY A WIDE RANGE OF FACTORS.

Certain foods, particularly those rich in histamine like fermented products, aged cheese, and alcohol, as well as food additives such as preservatives and artificial colours, are common culprits.

Environmental factors like pollen, mould, dust mites, and pet dander can also provoke reactions.

Temperature changes, whether due to extreme heat, cold, or rapid fluctuations, frequently activate mast cells.

Both emotional and physical stress, as well as trauma and even early life trauma and Chronic Inflammatory Response Syndrome (CIRS), can serve as significant triggers for MCAS symptoms.

Certain medications, such as NSAIDs, opioids, some antibiotics, and beta-blockers, may also worsen symptoms.

Infections, including viral, bacterial, and fungal, are known to cause flare-ups. Additionally, vigorous exercise or overexertion, exposure to chemicals like strong perfumes, fragrances, cleaning products, or cigarette smoke, and hormonal fluctuations during the menstrual cycle or pregnancy can all lead to symptom exacerbation.

Finally, insect stings or bites from bees, wasps, or mosquitoes are known to trigger severe mast cell reactions in some individuals.

Conditions Associated with MCAS

Mast Cell Activation Syndrome (MCAS) is often linked to several health conditions that involve chronic inflammation, immune system dysfunction, and hypersensitivity. These related conditions can either contribute to the development of MCAS or coexist due to shared biological mechanisms.

Below is a list of conditions associated with MCAS we commonly see in clinic :

Ehlers-Danlos Syndrome (EDS) and Hypermobility Spectrum Disorders
Connective tissue disorders like EDS are commonly seen alongside MCAS. Joint hypermobility, chronic pain, and autonomic dysfunction may be present, and mast cell instability may contribute to widespread symptoms beyond musculoskeletal concerns.

Postural Orthostatic Tachycardia Syndrome (POTS)
POTS, a form of dysautonomia, frequently overlaps with MCAS. It is marked by dizziness, rapid heart rate, and fatigue upon standing — symptoms that may be exacerbated by mast cell mediators affecting blood vessel tone and fluid balance.

Small Intestinal Bacterial Overgrowth (SIBO)
SIBO is a common gut condition that can trigger mast cell activation through microbial overgrowth and increased intestinal permeability. Many with MCAS report bloating, reflux, and food sensitivities that may be rooted in microbial imbalance.

Chronic Inflammatory Response Syndrome (CIRS) and mould-related illness
Exposure to biotoxins, especially from water-damaged buildings, may trigger both CIRS and mast cell activation. Clients often present with extreme reactivity, cognitive issues, and systemic inflammation, requiring careful environmental and immune support.

Long COVID / Post-viral syndrome
Post-viral syndromes, including long COVID, can induce a hyperactive mast cell state, leading to persistent fatigue, breathlessness, and immune dysregulation. MCAS support is often a key piece in recovery for these individuals.

Autoimmune disease
Conditions such as Hashimoto’s thyroiditis, lupus, and rheumatoid arthritis may occur alongside MCAS. Mast cell dysfunction may amplify autoimmune activity, creating overlapping inflammatory and immune-mediated symptoms.

Chronic Fatigue Syndrome (ME/CFS)
Many individuals with ME/CFS display signs of mast cell activation, including exertion intolerance, unrefreshing sleep, and cognitive dysfunction. Supporting mast cell stability may offer symptom relief in this complex condition.

Multiple Chemical Sensitivity (MCS)
Those with MCS often experience adverse reactions to fragrances, cleaning products, or pollutants. Mast cell instability is thought to underlie this heightened sensitivity, and calming the immune response can play a role in reducing symptom intensity.

Irritable Bowel Syndrome (IBS) and chronic gut dysfunction
Chronic bloating, cramping, diarrhoea or constipation may reflect underlying mast cell activity in the gastrointestinal tract. Addressing MCAS may lead to significant improvement in gut symptoms when standard IBS treatments fall short.

Interstitial cystitis / bladder pain syndrome
Painful bladder symptoms, urgency, and pelvic discomfort can be driven by mast cell release in the bladder lining. MCAS treatment may be particularly helpful when urological investigations show no clear cause.

Migraine and chronic headaches
Mast cell mediators like histamine and prostaglandins are known to contribute to vascular changes that can trigger migraines. Many clients with MCAS find that stabilising mast cells reduces headache frequency and intensity.

Dermatographia, eczema, urticaria, and other skin conditions
Skin-related symptoms are some of the most classic signs of MCAS. Chronic hives, itchiness, flushing, or visible welts after light pressure on the skin may indicate underlying mast cell reactivity.

Anxiety, panic disorders, and mood dysregulation
Mast cells reside in the brain and nervous system and can influence neurotransmitter balance. Many clients experience panic, anxiety, or mood swings that improve with appropriate MCAS support.

What can you do to manage MCAS?

LET'S FIRST ACKNOWLEDGE THAT MCAS IS A COMPLEX CONDITION.

It involves identifying and avoiding triggers such as specific foods, environmental factors, medications, or stress.

A low-histamine diet can be beneficial by avoiding foods such as fermented products, aged cheeses, processed meats, alcohol, and certain fruits and vegetables. The carnivore diet may also be helpful in reducing potential histamine triggers as well as inflammatory food proteins that may be exacerbating symptoms,.

Medications, including antihistamines (H1 and H2 blockers), mast cell stabilisers like cromolyn sodium, and leukotriene inhibitors, are often used to control symptoms in individuals who need the extra support. Supplements can also be really helpful to stabilise mast cells and reduce histamine levels.

Understanding and managing co-existing conditions like Chronic Inflammatory Response Syndrome (CIRS), autoimmune disease, Small Intestinal Bacterial Overgrowth (SIBO) or Postural Orthostatic Tachycardia Syndrome (POTS) is essential.

It is also important to consider the impact of stress, whether as a trigger or as a contributing factor. Stress reduction techniques like mindfulness, limbic system retraining or yoga can minimise activation due to emotional stress.

Histamine Intolerance

Histamine intolerance (HIT) occurs when the body struggles to break down excess histamine, leading to a range of symptoms that often overlap with mast cell activation syndrome (MCAS).

While MCAS involves the overproduction and inappropriate release of histamine and other inflammatory mediators by mast cells, HIT is specifically caused by a deficiency or dysfunction of the enzymes that degrade histamine, particularly diamine oxidase (DAO) and histamine N-methyltransferase (HNMT).

Symptoms of Histamine Intolerance

Since histamine plays a role in multiple bodily functions, symptoms can affect various systems and may fluctuate over time. These include:

Skin – Flushing, hives, itching, eczema-like rashes
Gastrointestinal – Bloating, nausea, diarrhoea, acid reflux
Cardiovascular – Palpitations, low blood pressure, dizziness
Neurological – Headaches, migraines, brain fog, anxiety, insomnia
Respiratory – Nasal congestion, sneezing, asthma-like symptoms

Symptoms often fluctuate and may worsen after consuming high-histamine foods such as fermented foods, aged cheeses, alcohol, and certain processed meats.

Conditions Associated with Histamine Intolerance

Histamine intolerance frequently coexists with other chronic health conditions, including:

Mast Cell Activation Syndrome (MCAS) – Since mast cells release histamine, unmanaged MCAS can worsen histamine intolerance.
Small Intestinal Bacterial Overgrowth (SIBO) – Gut dysbiosis can lead to excess histamine production and reduced breakdown.
Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD) – Increased gut permeability and inflammation may impair histamine degradation.
Ehlers-Danlos Syndrome (EDS) and Dysautonomia – Many individuals with connective tissue disorders experience histamine intolerance due to mast cell involvement.
Long COVID and Post-Viral Syndromes – Chronic inflammation and immune dysregulation can contribute to histamine-related symptoms.

How we can support you at the clinic:

At The Autoimmune Clinic, we understand that histamine intolerance is complex and highly individual. Our approach goes beyond simply reducing histamine exposure—we work with you to:

Identify your root causes – Using functional testing, we assess gut health, enzyme function, nutrient status, and immune balance.

Personalise your nutrition plan – We guide you through a tailored low-histamine diet while ensuring optimal nutrient intake.

Support histamine breakdown – Strategies to enhance DAO enzyme activity, improve gut health, and modulate mast cell function.

Address underlying triggers – From gut imbalances to chronic infections, we help uncover and resolve the factors contributing to histamine intolerance.

Improve resilience and tolerance – Our goal is not just symptom management, but long-term balance and improved quality of life.

If you’re struggling with histamine intolerance, MCAS, or related conditions, our team is here to support you with a science-based, integrative approach.

Frequently Asked Questions

Kharrazian Institute with Dr Datis Kharrazian:

Male and Female Hormone Imbalance Throughout the Lifespan Chronic Infections Clinical Strategies and Treatment Applications Mood and Anxiety Disorders Clinical Strategies and Treatment Applications Cardiovascular and Neurovascular Syndromes Clinical Strategies and Treatment Applications Childhood Development Disorders Clinical Strategies and Treatment Applications Chronic Fatigue and Pain Syndromes Clinical Strategies and Treatment Applications Cognitive Decline and Dementia Clinical Strategies and Treatment Applications Infertility, Prenatal Care, and Maternal Health Clinical Strategies and Treatment Applications Diabetes and Dysglycemia Clinical Strategies and Treatment Applications Neuroinflammation Clinical Strategies and Treatment Applications Hashimoto’s Clinical Strategies and Treatment Applications Autoimmunity Clinical Strategies and Treatment Applications Gastrointestinal Clinical Strategies and Treatment Applications Plus: Clinical Mastership Program: 100 hours of education with Dr Datis Kharrazian.
Institute for Functional Medicine (IFM):

Applying Functional Medicine in Clinical Practice - AFMCP Biotransformation Advanced Practice Module Cardiometabolic Advanced Practice Module GI Advanced Practice Module Immune Advanced Practice Module
The Shoemaker Protocol for Biotoxin illness:

Certified Proficiency Partner
The SIBO Doctor (Dr. Nirala Jacobi):

The SIBO Mastery Program with Dr Nirala Jacobi Navigating the Pediatric Gut with Dr Whitney Hayes & Dr Megan Taylor Mastering Inflammatory Bowel Disease with Dr Ilana Gurevich
Cogence Immunology with Dr Yannuck:

Most comprehensive training on functional immunology
AIP Certified Health Coach

Autoimmune Paleo Diet (AIP) Certification
Apex Seminars:

Mastering Blood Chemistry with Dr Eric Dorninger Mastering Brain Chemistry with Dr Eric Dorninger
Dr Jason Hawrelak:

Gastrointestinal Health Masterclass

We understand you may have questions about managing MCAS with our approach. Below are some common queries we receive:

Personalised Support for Mast Cell Activation Syndrome (MCAS)