Mast Cell Activation Syndrome or MCAS and its symptoms
Pain without a clear cause, fatigue that doesn't pass even after weeks of rest, skin reactions to foods that were previously tolerated, or sudden allergic attacks without an obvious trigger. This is exactly what the everyday reality looks like for people suffering from mast cell activation syndrome, abbreviated as MCAS. Although this condition is being discussed more and more, many doctors still don't know about it or confuse it with other diagnoses. The result is years of wandering from doctor to doctor, piles of examinations, and patients who begin to think they are simply making it all up.
Mast cell activation syndrome belongs to the so-called complex chronic diseases, the prevalence of which has been growing significantly in recent decades. It is not merely a physical disease – it affects a person's entire life, influencing their work, relationships, and psychological wellbeing. And although science has made significant progress in understanding this syndrome, the path to diagnosis is still long and exhausting for most patients.
Try our natural products
What are mast cells and why do they go haywire?
In order to understand what happens in the body with MCAS, it is first necessary to understand what mast cells are and what role they play in the human organism. Mast cells are specialised cells of the immune system found in virtually all tissues of the body – in the skin, mucous membranes of the respiratory tract, the digestive tract, the brain, and around blood vessels. Their job is to protect the organism against infections, toxic substances, and foreign bodies. When encountering a threat, they activate and release a whole range of chemical mediators, the most well-known of which is histamine.
Under normal circumstances, this reaction is desirable and precisely regulated. In people with MCAS, however, mast cells react excessively or entirely without apparent reason. They activate in response to stimuli that would cause no reaction in a healthy person – this can be a certain type of food, a scent, a change in temperature, physical exertion, stress, or even just the friction of clothing fabric. The result is a massive release of mediators that causes symptoms affecting literally the entire body at once.
It is precisely this multi-system nature that is one of the reasons why MCAS is so difficult to recognise. A patient comes to a doctor with abdominal pain, who then refers them to a gastroenterologist. Skin problems are handled by a dermatologist, fatigue by an internist, headaches by a neurologist. Each specialist sees only their piece of the puzzle and no one sees the whole picture. This fragmented approach to care is unfortunately typical and enormously frustrating for patients.
The symptoms of MCAS are truly varied and seemingly unrelated. The most common include:
- hives, skin redness and itching
- digestive problems – diarrhoea, cramps, nausea, reflux
- respiratory problems – nasal congestion, cough, shortness of breath
- neurological symptoms – brain fog, headaches, dizziness
- cardiovascular reactions – heart palpitations, drop in blood pressure, fainting
- fatigue and joint and muscle pain
- anaphylactic reactions without a clear allergen
It is precisely the combination of these symptoms, which come and go and change over time, that makes MCAS a diagnostic puzzle.
Why is MCAS only being talked about now?
Mast cell activation syndrome is not an entirely new discovery, but it is only in recent years that it has been gaining wider awareness among both professionals and the general public. The first diagnostic criteria for MCAS were formulated around 2010 by a group of leading allergists and haematologists. Since then, research in this area has developed significantly, although discussions about the precise definition and diagnostic criteria still exist. An overview of the current state of research can be found, for example, in the specialist database PubMed, where hundreds of scientific studies dedicated to mast cell diseases are now available.
One of the reasons why MCAS is coming to the forefront of attention right now is its apparent connection with other modern health challenges. Researchers have found that MCAS occurs surprisingly often alongside other complex chronic diseases, such as Ehlers-Danlos syndrome, postural orthostatic tachycardia syndrome (POTS), or myalgic encephalomyelitis. This trio is referred to in the specialist literature as the so-called "triad," and their co-occurrence suggests that they may share common biological mechanisms.
Special attention has also been drawn to MCAS in connection with the COVID-19 pandemic. A number of researchers point out that the symptoms of so-called long COVID – that is, persistent problems following infection – closely resemble the manifestations of MCAS. Some scientists even put forward the hypothesis that SARS-CoV-2 infection may trigger or significantly worsen MCAS in predisposed individuals. This area of research is still active and is yielding new findings that could help not only patients with MCAS, but also millions of people suffering from long COVID around the world.
Another factor contributing to the growing prevalence, or at least the growing visibility, of MCAS is changes in the environment and lifestyle. Chronic stress, air pollution, industrially processed foods, lack of sleep, and disruption of the gut microbiome – these are all factors that can contribute to immune system dysfunction, and therefore to mast cell hypersensitivity. It is no coincidence that MCAS is described as a disease of the 21st century – its prevalence is growing hand in hand with the modernisation of society and the changes it brings.
As leading American allergist and mast cell disease researcher Lawrence Afrin said: "MCAS is probably one of the most common chronic diseases that most doctors have never heard of." These words capture the paradox that patients face on a daily basis – the disease is real, widespread, and scientifically described, yet it remains on the margins of medical awareness.
How is MCAS diagnosed and treated?
The diagnosis of MCAS is demanding and requires a combination of clinical presentation, laboratory tests, and the exclusion of other diseases. The basic diagnostic criterion is the presence of typical symptoms affecting multiple organ systems, laboratory evidence of increased production of mast cell mediators, and a positive response to treatment targeting mast cells.
In practice, this means measuring tryptase levels in the blood – ideally during an acute reaction and then at rest – as well as monitoring other markers, such as histamine and its metabolites in urine. These tests are not always available or interpretable, because mediator levels can fluctuate and normalise in the short term. This is precisely why the experience of the physician and their ability to assess the overall clinical picture, rather than just an individual number in a laboratory result, plays a key role.
Treatment of MCAS is complex and highly individual. There is no single universal approach that works for everyone. The foundation consists of so-called mast cell stabilisers and histamine receptor blockers – that is, antihistamines and substances that prevent mast cells from excessive activation. Specifically, this involves a combination of H1 and H2 antihistamine blockers, sodium cromoglycate, or quercetin as a dietary supplement with natural stabilising effects.
Quercetin in particular, a naturally occurring flavonoid found in onions, apples, and kale, has attracted great interest from researchers and patients alike in recent years. Studies published in specialist journals suggest that quercetin can inhibit mast cell degranulation, the process by which mast cells release their mediators. Similar properties are attributed to other natural substances, such as lutein, resveratrol, or omega-3 fatty acids. For many patients with MCAS, natural dietary supplements have thus become an important part of everyday health care – not as a replacement for medical care, but as a complement to it.
Diet also plays an absolutely crucial role in MCAS. Many patients find that certain foods significantly worsen their symptoms, while others alleviate them. This typically involves the so-called low-histamine diet, which restricts foods with a high histamine content or substances that promote its release. These include fermented foods, aged cheeses, alcohol, tomatoes, spinach, and certain types of fish. Switching to a low-histamine diet does not mean giving up tasty and nutritious meals – with the right approach, one can eat diversely, enjoyably, and at the same time gently on one's own body.
Take the example of a thirty-year-old teacher from Brno who suffered for years from unexplained episodes of hives, stomach pain, and extreme fatigue. She underwent dozens of examinations and received diagnoses ranging from irritable bowel syndrome to anxiety disorder to gluten allergy. It was only after five years, and a chance encounter with an allergist specialising in mast cell diseases, that she finally received a diagnosis of MCAS. After starting treatment with antihistamines and adjusting her diet, her condition improved significantly. "I finally know it wasn't just in my head," she says. Her story is not exceptional – on the contrary, it is typical for thousands of patients around the world.
In addition to pharmacological treatment and diet, overall lifestyle care also plays an important role. Regular exercise at a moderate intensity, stress management through meditation or yoga, quality sleep, and minimising exposure to chemical substances in the home environment – all of this can contribute to reducing the overall burden on the immune system. Patients with MCAS often switch to natural cleaning products without aggressive fragrances, choose clothing made from natural materials, and pay increased attention to the composition of cosmetics and foods. This holistic approach to health care is not just a fashionable trend – for people with MCAS, it has a completely concrete and measurable impact on the quality of their everyday lives.
The psychological aspect is also an important consideration. Living with a disease that those around you cannot see and often do not understand is enormously challenging. Patients with MCAS face a lack of understanding from family, friends, and employers alike. Organisations such as The Mastocytosis Society provide not only information, but also a community of people with the same experience, which can be just as valuable for patients as medical care itself.
Mast cell activation syndrome thus compels us in many respects to reconsider how we approach chronic diseases in general. It shows how complex and interconnected the human immune system is, how important it is to listen to the body, and what a fundamental role environment, diet, and lifestyle play in maintaining health. For people living with MCAS, this disease is not an abstract scientific concept – it is an everyday reality that requires courage, patience, and a constant search for balance. And the more that becomes known about it, the fewer people will have to spend years searching for answers that they should have received much sooner.
