Mast Cell Activation Syndrome
Mast Cell Activation Syndrome (MCAS) Doctor in NYC
Mast Cell Activation Diagnosis and Treatment
Medically reviewed by Dr. Dean Mitchell, MD | July 25, 2026
Mast cell activation syndrome is a common, yet under-recognized, chronic multi-system disorder that occurs when mast cells inappropriately activate. Mast cells are present in virtually every tissue of the body and release mediators which can have a range of effects on other cells — causing a wide variety of symptoms. Most doctors are not trained to recognize the full picture of MCAS, which is why the average patient sees 10 or more specialists before getting a correct diagnosis.
Dr. Dean Mitchell has over 30 years of experience diagnosing and treating illnesses that are difficult for many doctors to identify. As a holistic, functional-medicine allergist and immunologist, he sees patients in person at his Manhattan and Rockville Centre, Long Island offices and via telehealth nationwide. He takes every patient’s full medical history himself — directly. There is no patient care team: no medical assistant, nurse, or physician-in-training who conducts the intake and relays it to him. You speak with Dr. Mitchell directly.
What are Mast Cells – and Why Do They Matter?
Mast cells are the immune system’s first responders. They are present in nearly every tissue in the body — the skin, gut, lungs, heart, and brain. When the body senses danger, mast cells are first on the scene. They release chemical signals that call in the rest of the immune system to fight back.
In a healthy immune system, that response is protective — it switches on when there is a real threat and settles back down afterward. In MCAS, that off-switch fails. The mast cells stay activated and keep releasing their chemicals even when there is no real emergency, which is what produces the wide range of MCAS symptoms.
Mast cells were first discovered in the 1800s by Nobel Prize-winning scientist Paul Ehrlich. For most of medical history, they were linked mainly to allergic reactions. That understanding has changed. Today Dr. Mitchell — who has worked with MCAS patients for over 30 years — sees mast cell activation as one of the most important and most overlooked areas in immune health.
“I remember thinking for many years — why would our bodies invent a cell that just gave people allergies? That didn’t make sense. COVID-19 changed how I see it. Mast cells are not allergy cells. They are primary immune defenders. When they get overactivated, they can affect every system in the body at once.” — Dr. Dean Mitchell, MD (MCAS webinar)
Symptoms Associated with MCAS
The most common symptoms associated with mast cell activation syndrome include:
- Skin Issues: hives, flushing, itching, rashes
- Gastrointestinal (GI) Issues: bloating, reflux, nausea, diarrhea
- Respiratory Issues: sneezing, wheezing, shortness of breath
- Cardiac Issues: palpitations, chest pain, low blood pressure
Dr. Mitchell has spent more than 30 years building a clear picture of how MCAS actually shows up in real patients. Based on his clinical experience:
- Gut symptoms: bloating, cramping, nausea, diarrhea, or reflux that doesn’t respond to standard treatment — gut symptoms appear in over 90% of his MCAS patients.
- Skin symptoms: hives, flushing, itching, or a reactive skin finding called dermatographism — skin symptoms appear in roughly 90%.
- Headaches: often not responding to regular migraine medication — headaches or migraine-type headaches appear in about 80%.
- Heart-related symptoms: a racing heart (tachycardia) or low blood pressure, which can cause dizziness or near-fainting when standing up quickly.
One symptom that surprises most patients is dermatographism. When Dr. Mitchell lightly strokes a patient’s skin with his fingernail during an exam, it turns red and raises up — almost like writing on skin. This tells him something important is happening below the surface. Most patients have no idea they have it until he shows them.
MCAS also shows up in ways patients are often embarrassed to mention — brain fog, memory problems, mood changes, anxiety after eating, or sensitivity to smells and chemicals. These are real, physical symptoms caused by mast cell chemicals crossing into the brain. They are not imagined, and they are not “just anxiety.”
If you feel that you have been sick forever; have trouble with allergies and asthma; get facial and chest flushing; suffer from skin rashes that come and go; regularly get brain fog and headaches; have overreactions to insect bites, bee stings and chemical intolerances; or suffer from poor wound healing and bruise easily you may have MCAS.
Factors that Can Cause MCAS
Mast cells can be triggered by many different things — and finding the specific trigger driving your symptoms is the core of how Dr. Mitchell approaches treatment.
Episode 49 — Mast Cells: How They Affect Vaccine, Drug and Food Allergies with Dr. Mariana Castells, Professor of Medicine, Harvard Medical School and Director of the Mastocytosis Center, Brigham and Women’s Hospital
Mast cells are the forgotten cells and play a key role in many allergic reactions. Harvard expert Dr. Mariana Castells provides the latest information on Mast Cell Activation Syndrome and how mast cells can be involved in a wide range of allergic reactions.
Medicines that can trigger mast cells to activate include
- Opioids: codeine
- Anesthesia
- Antibiotics
Other miscellaneous factors that can activate mast cells include
- Foods: nuts, shellfish, strawberries
- Mold
- Electromagnetic radiation: cell phones
- Temperature changes
What is Causing Your Mast Cells to Overactivate?
Most doctors treat MCAS symptoms. Dr. Mitchell does something different — he looks for the root cause. Why are the mast cells overactivated in the first place? That question drives everything.
“I always like to say the mast cells are kind of the top layer of the cake — they’re what’s reacting on the surface. But my job, as an immunologist and a medical detective, is to find out why they’re activated. Is it due to allergens? Toxic mold? An infection like Lyme disease or another tick-borne illness? Or a vaccine like the COVID vaccine? Finding that underlying cause is my real job.” — Dr. Dean Mitchell, MD (June 18 clinical interview)
In Dr. Mitchell’s clinical experience, MCAS almost never shows up on its own. Something is usually setting it off. The most common triggers he investigates:
Toxic Mold
Mold from water-damaged buildings is one of the most common triggers Dr. Mitchell finds in his MCAS patients. Mold releases toxic compounds called mycotoxins that can directly activate mast cells. Standard allergy tests do not pick this up — a patient can have a completely negative allergy panel and still have mold driving their MCAS. Dr. Mitchell uses urine mycotoxin testing to identify whether mold is a factor. This is a particularly common issue in older homes across New York City and Long Island, where water damage from leaky pipes or flooding can go unnoticed for years.
Candida Overgrowth
Candida is a yeast that lives naturally in the gut. When it grows out of control — often after antibiotic use or a high-sugar diet — it produces substances that can trigger mast cell reactions. Dr. Mitchell sees significant overlap between MCAS and Candida overgrowth, and notes that treating one without addressing the other often leads to incomplete results. He covers this in depth in his 2025 book, Conquering Candida.
Tick-Borne Infections
Tick-borne illnesses like Lyme disease can trigger or worsen MCAS. Dr. Mitchell tests for Lyme disease and co-infections such as babesiosis and bartonella when the clinical picture suggests they may be involved. This is especially relevant for patients in the New York and Long Island area, where the ticks that cause red-meat allergy syndrome (Alpha-Gal Syndrome) are also prevalent.
Unrecognized Allergens
Sometimes the trigger is a traditional allergen — dust mites, cats, dogs, or a specific food — that has never been identified because standard testing looked in the wrong direction. Dr. Mitchell uses allergy blood testing (called ImmunoCAP) to check for environmental and food allergens that may be contributing to ongoing mast cell activation.
COVID-19 and Post-Viral Illness
COVID-19 has been a significant driver of new MCAS cases. Dr. Mitchell began seeing patients who had never reacted to anything in their lives — and then, after COVID, were reacting to almost everything. The virus appears to activate mast cells in ways that can persist long after the infection is gone. This is a pattern he had not seen before COVID at this scale.
Stress and Hormones
Stress can directly activate mast cells — and so can hormonal changes. Dr. Mitchell notes that mast cells appear to have receptors for stress hormones and estrogen. Women often notice that their MCAS symptoms get worse around their menstrual cycle. Severe cases can even involve anaphylactic reactions tied to hormonal shifts, a rare condition called catamenial anaphylaxis.
“A lot of times, with mast cells especially, it’s not just one thing. It’s a combination. A patient may have had the COVID vaccine, and then got mold exposure, and whatever — it can be more than one thing that all of a sudden breaks the dam and the issues start happening. I call this the double or triple hit theory.” — Dr. Dean Mitchell, MD (June 18 clinical interview)
How Dr. Mitchell Diagnoses MCAS
Diagnosing MCAS is not straightforward. There is no single blood test that confirms it. Standard allergy panels usually come back negative. And because symptoms show up across so many different body systems, most doctors — who work within one specialty — never see the full picture.
By the time a patient reaches Dr. Mitchell — whether at his Manhattan or Rockville Centre, Long Island office, or via telehealth — they have typically already seen 10 or more doctors. Each one checked their corner of the problem and found nothing definitive. Dr. Mitchell’s approach is built around connecting those dots.
“The history is probably 90% of the way of making the diagnosis. I have to hear all the small details that give me clues. Additional laboratory testing, unfortunately, is not that helpful.” — Dr. Dean Mitchell, MD (June 18 clinical interview)
Dr. Mitchell takes the full history himself. There is no medical assistant gathering your information and passing it on. No intake form that gets summarized for him later. You sit with Dr. Mitchell and you tell him your story — because the small details matter. The timing of a reaction, what you ate, where you were, what happened right before symptoms started — these are the clues that point to the right diagnosis.
What Dr. Mitchell looks for in the exam room
One of the first things Dr. Mitchell does in the physical exam is test for dermatographism. He lightly strokes the patient’s skin — and in MCAS patients, the skin turns red and raises up almost immediately. He describes it as being able to write your name on someone’s back with just a fingertip.
“I do like to stroke the skin to test for dermatographia. I find that can be a reflection of what’s going on inside the body. It’s amazing how many people don’t realize they have this.” — Dr. Dean Mitchell, MD (June 18 clinical interview)
Lab testing — what Dr. Mitchell orders and why
Dr. Mitchell is direct about the limits of lab tests in MCAS. In the June 18 interview, he said plainly that he doesn’t order a lot of lab tests, because the history gives him 90% of what he needs. But there are specific tests he does run:
- Tryptase level — ordered to rule out mastocytosis (a different condition where the body has too many mast cells) and a related genetic condition called hereditary alpha-tryptasemia (alpha-HAT). A normal tryptase result does not rule out MCAS. Most MCAS patients have a completely normal tryptase level.
- Urine mycotoxin testing — to investigate whether mold exposure is driving the mast cell activation.
- Tick-borne illness testing — checking for Lyme disease and co-infections like babesiosis and bartonella when the history suggests they may be involved.
- Allergy blood testing (ImmunoCAP) — in specific cases, to check whether environmental allergens like dust mites, cats, or dogs are contributing.
On the older diagnostic standard that required a 20% rise in tryptase during an active reaction, Dr. Mitchell is blunt: it was never practical. A patient in the middle of a reaction cannot draw their own blood and rush it to a lab in real time, so he does not rely on it.
“Originally, the way you would supposedly make a definitive diagnosis was if there was a 20% rise in their baseline tryptase level. But who’s gonna measure that at the time of the reaction? It’s not like they can draw blood on themselves and bring it to the lab. So it was kind of a silly thing.”
— Dr. Dean Mitchell, MD (June 18 clinical interview)
How telehealth fits the diagnostic process
Dr. Mitchell sees MCAS patients from around the country via telehealth — and he notes that it works extremely well for this condition. Because history is 90% of the diagnosis, the conversation itself is the primary tool. Physical access to his office is not required to get an accurate assessment. For patients who cannot travel to Manhattan or Long Island, telehealth is a complete and effective option.
Episode 75 – Making the Difficult Diagnosis of Mast Cell Activation Syndrome with Dr. Tanya Dempsey, MD, founder and medical director of the AIM Center for Personalized Medicine.
Dr. Mitchell and Dr. Dempsey, a leading expert on Mast Cell activation Syndrome, discuss the approach to making the difficult diagnosis in conditions such as mast cell activation, toxic mold disease, candida overgrowth, and lyme disease. These are really complicated medical conditions.
What Is the Difference Between MCAS and Mastocytosis?
Mastocytosis and MCAS are two very different conditions that involve mast cells — which is why they are sometimes confused. Understanding the difference matters, because they have different causes, different lab findings, and different treatment paths.
Mastocytosis is a condition where the body produces too many mast cells. It is a hematologic — or blood-related — disease. In some forms, there are genetic mutations and abnormal findings in the bone marrow. The key diagnostic marker is a mutation called the c-KIT D816V, and patients typically have a persistently elevated tryptase level above 20 ng/mL. Mastocytosis is well-defined, relatively rare, and requires evaluation by a specialist.
MCAS is different in an important way. In MCAS, the number of mast cells is normal — they are just behaving abnormally. They overactivate and release their chemicals at the wrong times and in response to the wrong triggers. Most patients with MCAS have a completely normal tryptase level, even during a reaction. This is one of the main reasons MCAS goes undiagnosed — doctors look at a normal tryptase and conclude the mast cells are fine, when the actual problem is how those mast cells are behaving, not how many of them there are.
There is also a third condition worth knowing about: hereditary alpha-tryptasemia, or alpha-HAT. This is a genetic condition in which a person inherits an extra copy of the tryptase gene, which causes their baseline tryptase to run higher than normal. It is not mastocytosis and it is not MCAS — but it can cause similar symptoms and can be mistaken for both. Dr. Mitchell is familiar with this condition and considers it when a patient has a borderline elevated tryptase that does not clearly fit mastocytosis. He has noted that alpha-HAT is more common than previously thought, and that picking it up matters because it changes how you interpret lab results.
When Dr. Mitchell orders a tryptase level on a new patient, his goal is specifically to rule out mastocytosis and alpha-HAT — not to confirm MCAS. A normal tryptase result is actually what he expects to see in a true MCAS patient. It does not reassure him that the mast cells are fine. It tells him the patient likely does not have mastocytosis, which is a separate and more serious hematologic condition.
How Dr. Mitchell Treats MCAS
Most patients who reach Dr. Mitchell have already tried antihistamines — Claritin, Allegra, Zyrtec, Pepcid, the standard H1 and H2 blockers. Some got a little relief. Most did not get enough. The reason: antihistamines work after the mast cell has already released histamine. They are cleaning up a spill that has already happened.
“I show patients in my office — it’s like I have a cup of water on my desk, and if the table shakes and the water spills, using antihistamines is like getting paper towels and trying to blot out what’s already spilled. I like to use a compounded medication called ketotifen, which is a mast cell stabilizer. It actually stabilizes the mast cell — preventing it from releasing this constant histamine and other mediators. I get really dramatic improvement with a medication like that.” — Dr. Dean Mitchell, MD (June 18 clinical interview)
Dr. Mitchell’s Three-Step Approach
Step 1: Calm the system down. Before anything else, Dr. Mitchell looks at what is making the mast cells reactive and works to reduce the overall load. That means reviewing diet (high-histamine foods such as avocado, spinach, eggplant, aged cheeses, alcohol, and fermented foods), looking for mold exposure, checking for allergens, and investigating infections. It also means looking at the nervous system — the amygdala, or fear center of the brain, can get stuck in overdrive in MCAS patients and make everything worse. Dr. Mitchell references the work of Dr. Neil Nathan on limbic retraining and also discusses vagus nerve stimulation devices as options for appropriate patients.
Step 2: Stabilize the mast cells. Dr. Mitchell’s first-choice medication is compounded ketotifen — a mast cell stabilizer that is not commercially available as a pill in the US, so he has it made at a compounding pharmacy. Most patients notice improvement within one to two weeks. He also uses antihistamines in combination, leukotriene blockers, quercetin as a natural supplement, and in more severe cases Xolair (omalizumab) — an injectable biologic for patients who have been reduced to tolerating only a handful of foods.
Step 3: Find and treat the root cause. This is what separates Dr. Mitchell’s approach from most MCAS treatment. Once the mast cells are more stable, he digs into the underlying driver — the mold, the Candida, the tick-borne infection, the unidentified allergen. Stabilizing mast cells without addressing the root cause means patients stay on medication indefinitely. Dr. Mitchell’s goal is for patients to eventually not need medication at all — and most of them do not stay on it long-term.
The Low-Histamine Diet and MCAS
Diet is one of the first things Dr. Mitchell reviews as part of calming the immune system down. Not every MCAS patient reacts to dietary histamine — but for those who do, reducing high-histamine foods can meaningfully lower the frequency and intensity of reactions, especially in the early stages of treatment.
In the June 18 clinical interview, Dr. Mitchell identified four foods he considers the biggest histamine contributors for his MCAS patients:
- Avocado
- Spinach
- Eggplant
- Aged cheeses
Beyond those four, other common high-histamine foods worth watching include fermented foods (sauerkraut, kimchi, miso), alcohol — particularly red wine and beer — and leftover meat, which accumulates histamine as it sits.
Dr. Mitchell is direct about something most online low-histamine resources are not: not every MCAS patient needs to follow a strict low-histamine diet. Some patients react strongly to these foods. Others eat them without issue. Diet is something to test in the individual — if reducing histamine-rich foods is not producing noticeable benefit within a few weeks, restricting the diet further is unlikely to help and may simply make eating more difficult.
The goal is not a lifelong list of foods to fear. It is to identify which triggers apply to you specifically, reduce the overall histamine load while mast cells are being stabilized, and expand the diet again as treatment takes effect.
“Patients usually respond within a week or two. It does not take that long to see the benefit. And then I explain to them: you won’t need the medication if your mast cell stabilizes on its own — meaning if we remove the triggers. The more you calm it down, the more it stays in that equilibrium state. I don’t want them on medication for life, and most of them are not.”
— Dr. Dean Mitchell, MD (June 18 clinical interview)
What is the Difference Between MCAS, Histamine Intolerance, and Food Allergies?
These three conditions look similar on the surface. All of them can cause flushing, digestive trouble, hives, and headaches. But they are three different problems with three different causes — and they need three different treatments.
True food allergies are IgE-mediated. The immune system creates antibodies to a specific food protein — peanuts, shellfish, tree nuts. Standard allergy testing (skin tests and blood panels) is accurate for these, and reactions usually happen within minutes.
Histamine intolerance is an enzyme problem, not an immune problem. The body lacks enough of an enzyme called DAO to break down histamine that comes in from food. People with this issue tend to react specifically to high-histamine foods — avocado, spinach, eggplant, aged cheese, fermented foods, alcohol. Dr. Mitchell notes that this group is less common than MCAS patients in his practice.
MCAS is a system-wide immune condition. The mast cells overactivate in response to many different triggers — not just food — across multiple body systems at once. Standard allergy testing comes back negative. The pattern of reactions is broader, less predictable, and harder to pin down.
Many patients spend years being told they have food allergies when the real issue is MCAS or histamine intolerance. Dr. Mitchell’s training as a Board-Certified Allergist and Immunologist means he can evaluate all three simultaneously and identify the correct diagnosis — or the correct combination, since these conditions can and do overlap.
Can MCAS, Candida Overgrowth, and Mold Illness Happen at the Same Time?
Yes — and they do, regularly. Dr. Mitchell sees this combination frequently in his practice. These three conditions share a common thread: they all involve immune dysfunction, and each one can make the others worse.
“If somebody’s got Candida overgrowth but they’re also living in a toxic mold environment — now there’s a party going on between these fungi, and they gang up on the person and make them miserable. I can treat both. It’s just a little bit more complicated.” — Dr. Dean Mitchell, MD (MCAS webinar)
Mold produces mycotoxins that directly activate mast cells. Candida in the gut adds to the histamine load and can trigger additional reactions. When both are present at the same time as MCAS, patients tend to be the most reactive, the hardest to treat, and the most likely to have been dismissed by other physicians.
Dr. Mitchell uses urine mycotoxin testing to separate the mold and Candida picture. One compound — gliotoxin — shows up on the mold panel but is actually produced by Candida. Seeing elevated gliotoxin tells him Candida may be part of the problem, even when mold exposure is also present.
For these patients, treatment has to address all three conditions together — in the right sequence. Trying to treat MCAS without addressing the mold, or treating the mold without stabilizing the mast cells first, produces incomplete results. Dr. Mitchell has experience treating this exact overlap and has developed a protocol specifically for it.
Mast Cell Activation Syndrome: Unveiling the Hidden Truths About MCAS, Allergies, and Long COVID with Dr. Theoharis Theoharides, a leading expert on Mast Cell Activation Syndrome (MCAS)
Dr. Dean Mitchell and Dr. Theoharis Theoharides uncover the hidden power of mast cells—cells once thought to only trigger allergies but now linked to long COVID, chronic fatigue, neurological symptoms, and more. From surprising triggers like stress and foods to the latest treatment options, they dive deep into the fascinating science and practical solutions for those dealing with complex, chronic symptoms.
Why Patients Choose Dr. Mitchell for MCAS
Most MCAS patients have been to many doctors before they find Dr. Mitchell. They have been told their tests are normal. They have been referred to psychiatry. They have been given diagnoses that almost fit — irritable bowel syndrome, generalized anxiety, fibromyalgia — but never quite explained the full picture. What is different about coming to Dr. Mitchell is both what he knows and how he works.
- Over 30 years treating complex immune conditions that most physicians are not trained to recognize — including MCAS, mold illness, Candida, Lyme-related immune dysfunction, and Long COVID. He was seeing these patterns before they had widely accepted names.
- He takes your full medical history himself. Every time. You speak directly with Dr. Mitchell — not a medical assistant, nurse, or physician-in-training who relays your information to him. There is no patient care team in between. The history is 90% of the diagnosis, and he takes it personally.
- He is a Board-Certified Allergist and Immunologist with a holistic, functional approach. He has the diagnostic tools of conventional medicine and the root-cause thinking of functional medicine — both in the same consultation.
- He hosts The Smartest Doctor in the Room podcast with over 230 episodes featuring some of the world’s top researchers in mast cell biology, mold illness, Candida, Long COVID, and functional immunology. He brings those conversations directly into his patient care.
“If you understand mast cells, you understand inflammation — and if you understand inflammation, you understand medicine. One of my professors said that to me early in my career. The more I have worked with these patients over 30 years, the more I believe he was right.” — Dr. Dean Mitchell, MD (June 18 clinical interview)
Dr. Mitchell sees patients in person in Manhattan and Rockville Centre, Long Island, and via telehealth for patients anywhere in the country. Telehealth works well for MCAS because the history is the most important part of the consultation — and that can happen anywhere.
Patient Testimonials
There are absolutely no words that are adequate to thank you for your extraordinary diagnostic skill and for the care and attention that you have lavished on me. As you know, I had seen at least 10 doctors before I was lucky enough to make your acquaintance. I have felt so sick for so long that I had forgotten what it was like not to feel so terribly ill. Whatever you did for me, I believe and hope that the medicine you prescribed is making a difference. I have felt better for the last two days that I have been taking your medication and I am deeply deeply grateful to you. I am stunned that you cared enough to call me last night at 7:00 PM. That is definitely above and beyond the call of duty. I just want you to know what an amazing and wonderful doctor you are and that I will NEVER forget your kindness and expertise. Thank you so very very much.
Dr Mitchell and his staff are excellent! I have been a patient for many years , too many to count . The staff has always been extremely helpful . Dr Mitchell was able to get me past , prior to seeing him, many seasons of allergies colds and asthma . With his help and advice I no longer stress about colds and allergies because I know I am in good hands .
I have been seeing Dr. Dean Mitchell for over a year now for pain management, and treatment. He has been incredibly kind and knowledgeable from the start, he takes time to listen and has gone above and beyond in regards to my health. The excellent care I have received at Mitchell Medical Care Group has helped to reduce and improve symptoms of pain I have struggled with for years, and the warm presence of the staff constantly make me feel welcome in the office.
I found the Drs. Dean and Ricki Mitchell to be very knowledgeable, compassionate and have truly helped in finding the root cause of my medical condition by thinking outside of the box. I am now on my road to recovery ❤️ I am so very grateful to have found them. The facility and staff are excellent and I highly recommend Mitchell Medical Group.
I can't overstate it: Dr. Dean Mitchell changed my life! I'm about five months into my Candida treatment and my skin looks and feels better than it has ever been. Everyone who works in his office is lovely and pleasant to deal with. I have recommended Dr. Mitchell to friends and would recommend his care to anyone!! His wonderful, caring practice has restored my faith in the medical community. Thank you, Dr. Dean!!
I have been seeing Dr. Mitchell and the other staff for over two years now. I go monthly for an IV treatment and to meet with the staff. Dr. Mitchell and his team have significantly helped with my healing process. They are always friendly, attentive, and genuine and I truly enjoy going to each Meeting. They are all extremely knowledgeable and have taught me how to correctly better my health and wellness. I highly recommend their office.
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Frequently Asked Questions About MCAS
What is mast cell activation syndrome (MCAS)?
Mast Cell Activation Syndrome (MCAS) is a condition in which mast cells become overactivated and release excessive chemical compounds throughout the body, causing recurring symptoms across the skin, gut, lungs, heart, and brain simultaneously. There is no single blood test that confirms MCAS. Diagnosis is based on clinical history, physical exam findings, and response to treatment. Dr. Dean Mitchell diagnoses and treats MCAS at his Manhattan and Long Island offices and via telehealth nationwide.
What are the most common symptoms of MCAS?
Common MCAS symptoms include hives, flushing, skin that reacts to light pressure (dermatographism), bloating, cramping, diarrhea, nausea, reflux, brain fog, headaches, anxiety or palpitations after eating, nasal congestion, wheezing, low blood pressure, and near-fainting. In Dr. Mitchell’s clinical experience, gut and skin symptoms appear in over 90 percent of patients and headaches affect about 80 percent. The pattern of symptoms occurring across multiple body systems at once is what distinguishes MCAS from ordinary allergies.
How is MCAS diagnosed?
Dr. Mitchell considers the full patient history to be roughly 90 percent of what is needed to diagnose MCAS, and he takes that history himself in every consultation. He also checks for dermatographism during the physical exam. Lab tests including tryptase levels, urine mycotoxin testing, and allergy blood panels are ordered selectively. A normal tryptase result does not rule out MCAS. Response to a mast cell stabilizer within one to two weeks is itself an important diagnostic signal.
Why does MCAS go undiagnosed for so long?
MCAS symptoms spread across many body systems, and conventional medicine evaluates each system separately. No single specialist sees the full picture. Standard allergy tests also come back negative in MCAS, leading many doctors to dismiss patients or refer them to psychiatry. The average patient sees 10 or more doctors before getting an accurate diagnosis. Dr. Mitchell at Mitchell Medical Group in New York City looks at the complete clinical picture in every consultation.
What is the difference between MCAS, histamine intolerance, and food allergies?
Food allergies are IgE-mediated immune reactions to specific proteins, accurately identified by standard allergy testing. Histamine intolerance is an enzyme deficit causing dietary histamine to build up after eating high-histamine foods. MCAS is a broader condition where mast cells overreact to many triggers across multiple body systems simultaneously, with standard allergy testing usually negative. These conditions can overlap. Dr. Mitchell at Mitchell Medical Group is trained to distinguish between all three.
Is there an MCAS specialist in New York City?
Yes. Dr. Dean Mitchell is a Board-Certified Allergist and Immunologist who has been diagnosing and treating MCAS for over 30 years. He sees patients in person at his Manhattan office and his Rockville Centre, Long Island office. Dr. Mitchell takes every patient’s full medical history himself directly in every consultation. There is no medical assistant or physician-in-training who conducts intake on his behalf. Telehealth consultations are available for patients throughout New York State and nationwide.
Where in Manhattan can I see a doctor for MCAS?
Mitchell Medical Group’s Manhattan office sees patients with MCAS, Candida overgrowth, mold illness, chronic hives, and complex immune conditions. Dr. Dean Mitchell conducts every consultation personally with over 30 years of experience. A second office is in Rockville Centre on Long Island. Telehealth appointments are available for patients who cannot travel. Scheduling is at mitchellmedicalgroup.com/contact.
Do patients on Long Island have access to Dr. Mitchell for MCAS?
Yes. Dr. Mitchell’s Rockville Centre office on Long Island sees the same complex immune conditions as his Manhattan practice. Long Island patients with older homes, basement moisture, or storm-related water damage should know that mold exposure is one of the most common MCAS triggers Dr. Mitchell investigates. Urine mycotoxin testing can identify whether mold is involved. Telehealth is available for follow-up care.
Can mold exposure trigger MCAS?
Yes. Mold produces mycotoxins that directly activate mast cells, and this does not show up on standard allergy tests. A patient can have a completely negative allergy panel and still have mold driving their MCAS. Dr. Mitchell uses urine mycotoxin testing to evaluate mold as a factor. He has documented cases in which MCAS symptoms resolved substantially after identifying hidden mold in patients’ homes, often unknown to the patient, in New York City and Long Island.
Can MCAS cause brain fog and fatigue?
Yes. Brain fog and fatigue are among the most commonly reported MCAS symptoms. Mast cell chemicals can cross into the brain and nervous system, slowing cognitive function and causing persistent tiredness. These are real, physical symptoms, not imagined or anxiety. They are also the most likely to be dismissed by doctors because they do not appear on standard tests.
What is the connection between MCAS and Long COVID?
COVID-19 appears to trigger mast cell overactivation in some patients, and this can persist after the infection is gone. Dr. Mitchell began seeing post-COVID patients who had never reacted to anything before and were suddenly reacting to almost everything. Post-viral MCAS patients often present with brain fog, fatigue, new food and chemical sensitivities, and episodic flushing or palpitations. MCAS-specific treatment targeting mast cell overactivation can help these patients.
Can MCAS cause anxiety?
MCAS can produce symptoms that closely resemble anxiety, such as racing heart, flushing, and sudden dread, especially in the 15 to 30 minutes after eating. This is a direct result of mast cell chemicals affecting the nervous system, not a psychological condition. Many MCAS patients receive psychiatric diagnoses before anyone connects these symptoms to their immune system.
Is MCAS an autoimmune disease?
No. MCAS is not an autoimmune disease. Mast cells are primary immune defense cells that do not attack the body’s own tissue. MCAS does not cause positive ANA test results. Immunosuppressive medications used for autoimmune diseases are not appropriate for MCAS. This is a condition of immune overactivation, not immune self-attack.
Does sublingual immunotherapy (allergy drops) help with MCAS?
Allergy drops, also called SLIT or sublingual immunotherapy, can be a useful part of MCAS treatment when mast cell activation is partly driven by identifiable allergens like dust mites, pollen, pet dander, or certain foods. They work by gradually retraining the immune system’s response to those triggers. They are not a universal MCAS treatment, but for the right patient they can reduce overall immune reactivity. Dr. Mitchell evaluates each patient individually to determine whether allergy drops fit their plan.
How long does MCAS treatment take?
Most patients notice real improvement within one to two weeks of starting a mast cell stabilizer like ketotifen. For longer-term improvement, especially when an underlying cause like mold or Candida is being addressed, meaningful change typically takes three to six months. Dr. Mitchell’s goal is not to keep patients on medication indefinitely. As underlying triggers are reduced, most patients can reduce or stop medication over time.
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