Mast Cell Activation Syndrome: What it is and Symptoms

Have you ever experienced unexplained symptoms that doctors can’t seem to diagnose? You might have Mast Cell Activation Syndrome (MCAS). In this article, we’ll explain what MCAS is and how it affects the body. We’ll also discuss the triggers for mast cell overreaction and common signs and symptoms associated with MCAS.

Quick and simple first, technical discussion after.

MCAS is a condition where your body triggers allergic reactions even when you have no “allergy” to the trigger. These symptoms can range in severity, with reactions as minor as seasonal allergies (stuffy nose, itchy eyes, etc.), all the way to full blast lethal anaphylactic shock.

If you’re wondering whether or not you have MCAS, we have an article dedicated to helping you figure it out: Do I have Mast Cell Activation Syndrome (MCAS)? The Answer, In Plain English. There’s no technical medical jargon there, so it should be a quick and easy read.

The article below will be a little more technical, so if that’s what you’re looking for, read on.

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What “Mast Cell Activation Syndrome” Means

Let’s take those four words bit by bit.

We’ll start with the first two words: mast cell. Your body is teeming with these little guys called mast cells. They’re part of your immune system, and when they work correctly, they keep you safe from things that would make you sick. White blood cells are like the little cellular soldiers of the immune system, and mast cells are a type of white blood cell. In fact, mast cells are kinda like the special-forces ninja-assassin commando-unit of the immune system army.

Next: activation. So your mast cells float around in your body, ready and alert for danger. When they find some kind of microbiological bad guy, they “activate.” They go beast mode. Your immunological special-forces team says “GO GO GO!” And they go hard. Normally this keeps you safe from invaders.

When it comes to MCAS, however, your special-forces team is full of mavericks. Sometimes they correctly identify a real enemy, but they OVER react, and instead of snipers surgically striking viruses, it’s bazookas blasting in all directions. Your own body takes collateral damage. Sometimes your mast cells misidentify a friendly as an enemy. Maybe when you eat blueberries, your mast cells think you’re being poisoned, so they GOGOGO, and again your body is collateral damage. The worst is when your mast cells just go rogue and attack your own body for no real reason at all – cellular civil war.

Next: syndrome. The dictionary doesn’t really tell the whole story, but we’ll start there. “Syndrome” refers to a group of conditions that usually occur in a pattern together.

Let’s look at an example not related to MCAS.

There’s a pattern of thinking that successful people sometimes develop where they feel their success is accidental, or maybe fraudulent. They think they’re not worthy of, or didn’t really earn their success, even if they really did earn it, really do deserve it. That pattern of thinking we refer to as “impostor syndrome.” I guess we could call it “impostor feelings,” but that wouldn’t completely describe the thing, because it’s more than just feelings. It’s also a pattern of behavior, where people belittle their own achievements, excessively attribute their success to others who helped a little along the way. They sometimes take this pattern of behavior all the way to a self-destructive place, where they subconsciously sabotage themselves going forward. The phenomenon is a complex mixture of feelings, speech patterns, and behaviors, and there’s no word in English that encompasses all of that as perfectly as “syndrome.”

But when doctors use that word, it means something a little extra. In medicine, “syndrome” refers to a pattern of symptoms occurring for reasons doctors haven’t figured out yet. That’s why there’s no “broken bone syndrome.” If you step on black ice on a wintery night, fall down and break a bone, it’s not hard to identify the problem.

But when you have a bunch of symptoms that doctors can’t explain (allergic reactions without allergies) … and if you’re not alone, and in fact hundreds, maybe thousands, maybe millions of people all have the same symptoms … well then doctors know something is going on. But if they can’t figure out what is going on, or why, then that mystery is labeled a “syndrome.”

This can be confusing, though, when it comes to MCAS. If they know mast cells cause the problems, why do they call it a syndrome? Well, they know the Mast Cell Activation Syndrome symptoms are caused by mast cells, but they don’t WHY the mast cells do that. That’s the big mystery. If they figured out that mast cells go rogue because of sliced bread, then it wouldn’t be a syndrome anymore, and they would call it Sliced Bread Mast Cell Disease. For now, though, it’s a syndrome.

Mast Cells: What Are They, and Where Are They?

Mast cells are a type of white blood cell, and they live all throughout your body. They’re made in the bone marrow, and then travel to where they’re needed. Every part of you is protected by mast cells, but they assemble in larger numbers where you most need defense: your vital organs, your connective tissue, and any place where your body touches the outside world.

If we continue with our soldiers analogy from before, then you’re an island nation, with a coast guard protecting your perimeter, and a national guard protecting the interior.

The “coast guard” mast cells protect all the places where you interact with the external environment. So there’s a lot of mast cells in your skin to protect you from things you touch or get cut by. They’re in your nose and lungs to protect you from stuff you breathe. They’re in your mouth and digestive system to protect you from what you eat and drink. They’re in your eyes, which always touch the air. They’re in all your hair follicles, from the top of your head to the knuckles of your toes. And they’re in your genitals … for obvious adult reasons.

The “national guard” mast cells protect all your guts. They’re in all your vital organs: the liver, kidney, heart, etc. They’re in your brain, protecting your mind from pathogens and contaminants that pass through the “blood/brain barrier.” They’re in all your connective tissue: your joints, tendons, ligaments. They’re in and around all your blood vessels. They’re scattered throughout your entire nervous system.

Basically, they’re everywhere. This is why MCAS has the potential to affect nearly every part of your body.

Mast Cells: What Do They Do?

MCAS affects the body by inducing symptoms related to mast cell mediator release. Mast cells, when activated, release a multitude of substances, including histamine, prostaglandins, cytokines, and tryptase, among others. These mediators have diverse effects on different organ systems, resulting in the wide range of symptoms experienced by individuals with MCAS.

Let’s discuss how mast cells do this.

Mast cells are roughly spherical. Inside, they have an arsenal of bioweapons just waiting to be released. Those bioweapons include some things you’ve heard of, and others you might not have, and we’ll cover those here. The arsenal sits inside the cell as a collection of around 100 granules of “mediators” (or, like, 100 nuggets of chemicals and proteins).

In this case, the word “mediator” is another bit of medical lingo with a specific meaning: It’s something that causes an effect and, while it’s doing that, also controls what type of effect occurs, and how strong that effect is. Think of it like your home’s thermostat, which mediates the temperature in your house. When your thermostat is activated, it causes an effect (changing the air temperature), by controlling which effect occurs (heating or cooling), and by controlling how strong the effect should be (68° F, or 72° F).

The granules in your mast cells control several vital functions of both your immune system, and also your healing/repairing system. The mediator in a mast cell most people have already heard of is histamine, a chemical which causes allergic reactions (people commonly take Antihistamines to fight seasonal allergies, for example). There’s also tryptase, another allergic-reaction chemical. The granules can contain heparin, which is a natural blood thinner. There are also granules of chondroitin sulfate, which is sort of like organic construction material, mostly found in cartilage like your nose or ear, but useful for all sorts of things in the body. There are several other mediators found in mast cells, but the last one we’ll mention is cytokine, because you may have heard about “cytokine storms” in relation to COVID-19. Cytokines are involved in a variety of inflammatory conditions and, while that’s a good thing in the right amount, an excess of cytokines can be harmful, or even deadly.

That’s what’s going on inside a mast cell.

All along the outside, however, there’s more going on. Mast cells have sensors watching for a signal to unleash those bioweapons. These sensors are chemical receptors that line the exterior of the cell wall, triggered by touch. If your mast cell bumps into something the sensors recognize as “bad,” then the mast cells are triggered to “activate.” Your body learns with experience what sorts of things to watch out for, and so your mast cells’ sensors are finely tuned. When activated, your mast cell “degranulates.” Quite simply, it dumps all those granules of mediators into your system, into your tissues and blood stream.

When Mast Cells Overreact

When mast cells detect a threat, they release mediators, like histamine, which triggers inflammation. Mast cells are an essential part of the immune system, playing a crucial role in allergic reactions and defense against pathogens. However, in individuals with MCAS, these mast cells become hyperactive, leading to an inappropriate release of mediators, even in the absence of a clear cause or stimulus.

When mast cells overreact, it leads to a range of symptoms and complications. Understanding the triggers for mast cell overreaction is crucial in managing mast cell disorders. It is important to note that symptoms of MCAS can be triggered by various factors, including certain foods, stress, medications, environmental factors, and infections. The exact triggers can vary from person to person.

This overactivation of mast cells can contribute to the severity of Mast Cell Activation Syndrome symptoms. Identifying and avoiding these triggers often plays an important role in managing symptoms and improving quality of life for individuals with MCAS.

Signs and Symptoms of Mast Cell Activation Syndrome

Understanding the wide range of symptoms associated with mast cell activation syndrome is crucial. Mast cell mediators, including histamine, can cause symptoms throughout the body, affecting multiple organ systems. It’s important to note that MCAS is a multi-systemic condition, where two or more body systems are affected.

While mild and manageable symptoms may persist for an extended period, events like infections, surgeries, or illnesses can lead to a significant increase in symptom severity or frequency.

Symptoms of Mast Cell Overreaction

If you’re experiencing symptoms of mast cell overreaction, it’s important to understand the potential systemic effects that mast cell disorders can have on your body. These may include symptoms such as tachycardia (rapid heart rate) and low blood pressure.

The syndrome presents with various symptoms, affecting various organ systems, including the gastrointestinal tract, skin, cardiovascular, and respiratory systems. Common symptoms of MCAS include abdominal pain, flushing, itching, hives, diarrhea, bone pain, and fatigue. These symptoms can be chronic, and long-lasting, and often result in a reduced quality of life for affected individuals.

Dermatologic (Skin)

Mast cells play a significant role in the skin system. When mast cells are activated, they release mediators like histamine, which can have an impact on the skin. Dermatologic symptoms associated with mast cell activation syndrome include:

• hives
• pruritus (itching)
• urticaria (raised, itchy welts)
• angioedema (swelling)

These dermatologic symptoms serve as indicators of mast cell activation syndrome. Identifying these symptoms is crucial for diagnosing and managing this condition.

Gastrointestinal (Gut)

Mast cells are present in the gut and contribute to various gastrointestinal symptoms. Moreover, MCAS can cause complications in the intestines, bladder, and other organs. Identifying gastrointestinal symptoms is important in recognizing potential mast cell activation. Histamine and other mediators released by mast cells can impact the gut, leading to:

• abdominal pain
• diarrhea
• nausea

Neurologic (Nervous System)

There are numerous neurological symptoms that can present when mast cells are causing inflammation.

• difficulty concentrating
• brain fog
• memory problems
• headaches or migraines
• dizziness
• numbness or tingling
• nerve pain
• mood swings
• anxiety and depression
• heightened sensitivity to light, sound, and smells

These are common neurologic symptoms. with Mast Cell Activation Syndrome that can have a significant impact on day-to-day living. Understanding these neurologic symptoms is crucial in diagnosing and managing mast cell activation syndrome.

Musculoskeletal (Muscles & Bones)

Difficulty with coordination and balance may be a common early symptom of someone who may have mast cell activation syndrome. Later in life, patients may experience muscle pain, cramps, and weakness, which can greatly affect their daily activities. Over time, these symptoms worsen to the point of joint pain, stiffness, limited range of motion, and swelling. Additionally, mast cell activation syndrome can lead to bone pain, osteoporosis, and an increased risk of fractures.

Respiratory (Lungs)

Early symptoms in childhood or adolescence may include respiratory conditions, such as cough and asthma, due to mast cell activation. With the impact of triggers, leading to greater inflammation, these may worsen to shortness of breath or wheezing. Other respiratory symptoms may include sinus congestion, post-nasal drip, sneezing, chest pain, tightness, and pressure. Additionally, recurrent respiratory infections can be associated with mast cell activation. It’s important to address these symptoms and seek appropriate medical care.

Cardiovascular (Heart)

Mast cell disorders can cause a range of systemic symptoms affecting the cardiovascular system. These include tachycardia (rapid heart rate), palpitations, and even low blood pressure, orthostatic hypotension, and syncope (fainting). Chest pain, angina, and heart arrhythmias may also be experienced. Edema and fluid retention can lead to swollen extremities, while poor circulation and blood clotting disorders may further complicate cardiovascular function. It is important to recognize and address these symptoms to ensure proper management of mast cell activation syndrome.

Naso-ocular (Nose & Eyes)

Runny nose, nasal congestion, and sneezing are common symptoms of mast cell activation syndrome (MCAS). Itchy, watery, and bloodshot eyes can also occur due to mast cell overreaction. Some individuals may experience eye pain, pressure, and sensitivity to light. Additionally, sinus pain, pressure, and inflammation may be present. Allergic rhinitis, conjunctivitis, and blepharitis are often associated with MCAS. These naso-ocular symptoms can significantly impact an individual’s quality of life and require proper management.

Lymphatic System

The lymphatic system plays a crucial role in our body’s immune response. It includes several components such as lymph nodes, lymph vessels, and lymphocytes. In the context of mast cell activation syndrome (MCAS), the lymphatic system can be affected in various ways. MCAS can lead to enlarged lymph nodes, lymphedema (swelling due to fluid build-up), and an increased number of lymphocytes in the blood (lymphocytosis). Additionally, MCAS can cause recurrent infections and immune system dysfunction, leading to impaired lymphatic system function. Inflammation, histamine release, and allergic reactions are common in MCAS, further impacting the lymphatic system. The impaired immune cell function and mast cell activation associated with MCAS can disrupt the normal functioning of the lymphatic system. It is important to note that individuals with MCAS have an increased risk of anaphylaxis and other complications related to mast cell disorders.

Systemic (Whole Body)

Fatigue, low energy, and chronic pain are common symptoms experienced by individuals with mast cell activation syndrome. Flushing, redness, and hot flashes may also occur, along with swollen lymph nodes, fevers, and night sweats. It’s important to note that there is a risk of anaphylaxis, a severe allergic reaction, in mast cell activation syndrome. These systemic symptoms can greatly impact daily life and quality of life for those with this condition. Understanding and managing these symptoms is crucial in managing mast cell activation syndrome.

Could Unexplained Symptoms Be MCAS?

Recognizing the potential of mast cell activation syndrome (MCAS) in unexplained symptoms is important. Each person’s experience with MCAS may vary due to its complex pattern of symptoms. It is crucial to consider MCAS as a possible cause for patients with symptoms that lack a clear explanation.

In conclusion, it’s important to understand that mast cell activation syndrome (MCAS) is a complex condition with a wide range of symptoms. The symptoms can affect various systems in the body, including the skin, gut, nervous system, muscles and bones, lungs, heart, nose and eyes, and even the entire body. Identifying and understanding these symptoms is crucial for proper diagnosis and treatment. If you are experiencing unexplained symptoms that could be related to MCAS, it is important to consult with a healthcare professional who specializes in this condition. They can help determine the underlying cause and develop a personalized treatment plan to manage your symptoms and improve your quality of life.

Remember, you are not alone, and there is support available to help you navigate through this journey.

The article we referenced above, Do I have Mast Cell Activation Syndrome (MCAS) the Answer, In Plain English, gives a thorough list of the symptoms

Next: activation. Mast cells float around in your body waiting for something to react to, something “bad” that they can attack.

The information provided in this content is intended solely for educational and informational purposes. It is not meant to serve as medical advice or replace the guidance of your physician. We strongly encourage all readers to consult with their healthcare providers for any specific medical concerns. Hearts and Beaches and its publishers do not assume responsibility for any health outcomes resulting from the use of this information. Individuals taking prescription or over-the-counter medications should seek advice from their doctors before starting any new diet, supplement, or lifestyle changes.

Common MCAS Questions