Your Doctor Can't Find What's Wrong? It Might Be MCAS

What if headaches, anxiety, brain fog, insomnia, weird skin rashes, congestion, bloating, palpitations that you've been chasing for years aren't all a bunch of different separate problems? What if they're all coming from the same place? And what if some of the foods you've been told are healthy, like avocado, spinach, tomatoes, kombucha, even bone broth, are quietly making things worse? Well, today we're going to dive deep into one of the most overlooked, most misunderstood conditions in modern medicine called mast cell activation syndrome. It has to do with histamines, which is what gives hives, but it's much more than that. It's also known as MCAS or MCAS, mast cell activation syndrome. Now what we're gonna cover is a lot. We're gonna cover what mast cells actually do, why they sometimes go haywire. Mast cells are a type of white blood cell. How I diagnose MCAS in my practice, and most importantly, how we treat it. Supplements, herbs, medications, how we regulate the nervous system, and yes, even something weird called helminth therapy, otherwise known as worms. We're going to talk about that. If you've been told your labs are, quote, normal, but you know something is wrong, well, this conversation may finally help you connect the dots. So let's dive in. This episode was brought to you by Function. Get access to over 160 lab tests annually at functionhealth.com/Marc. Start with histamine. Most people hear histamine and think allergies, antihistamines, itchy eyes, a runny nose. That's just a sliver of the story. Histamine is a messenger your body makes every single day. It regulates immunity. It stimulates stomach acid. It acts as a neurotransmitter and it helps you run your sleep-wake cycle. You need it to survive. The trouble starts when histamine accumulates faster than your body can break it down. And when it does, The symptoms show up in places that seem completely unrelated. A headache here, anxiety there, insomnia, hives, congestion, bloating, a racing heart. And that's why this goes unrecognized for years. The symptoms don't point anywhere obvious. I think about it as a balance between 3 things: how much histamine your body produces, how much you take in from food and the environment, and how well you clear it. When those are in balance, you're fine. When they're not, Symptoms emerge. Now picture a bucket. Food adds to it. So does stress. So does poor sleep. So does allergy season. So does hormonal shifts. So does gut inflammation and infections. When the bucket is half full, you feel fine. When it overflows, you don't. That's why you can eat a food one day and feel great and then react to the same food a week later. It rarely is just the food. It's a total load of everything. So let's talk about mast cells. Where does histamine come from inside your body. A major source is a specialized immune cell called the mast cell. Now, the mast cells sit in your skin, in your gut, in your lungs, and around your blood vessels and nerves, right at the borders with the outside world. When they sense a threat, they release histamine and dozens of other inflammatory mediators to coordinate a response. In a healthy system, it's elegant, it's protective. In MCAS, or mast cell activation syndrome, or just overactive histamine system, the mast cells become hair-triggered. They release their mediators inappropriately, excessively, and in response to things that shouldn't provoke them— food, smells, temperature changes, stress, hormones, exercise. This is the key distinction. Histamine intolerance is often about clearance. Your body can't break histamine down fast enough. MCAS is about the cells themselves. They're firing when they shouldn't because the mast cells have been Every organ system. MCAS can look like almost anything. In your skin, it can be flushing, hives, and itching, writing on your skin when you scratch it, called dermatographia. It can be in your gut with bloating, cramping, reflux, diarrhea, sudden food reactions. It can be in your cardiovascular system from palpitations, blood pressure swings, lightheadedness. It can be neurologic, like brain fog, anxiety, headaches, insomnia. It can be respiratory systems like congestion, throat tightness, wheezing. A hallmark is it's a multi-system problem and it's episodic. It flares and it settles. And that pattern is a clue. Now, why does this occur more in women? Well, one of the most important developments of recent years is understanding how closely histamine and estrogen are linked. Estrogen stimulates mast cells to release histamine. Now histamine in turn can promote more estrogen activity. The two amplify each other. Like a conversation getting progressively louder. Now, for many women, that explains symptoms long dismissed as just, quote, hormonal— PMS, cyclical migraines, breast tenderness, mood changes, heavy periods, sleep disruption, worsening allergies. The clue is timing. If your symptoms track your cycle and they're worse before your period, around ovulation, or unpredictable in perimenopause when estrogen swings erratically, histamine and mast cells are worth investigating. Histamine is really the whole story, but it's often a missing piece. Here's how I diagnose MCAS, and here's where it gets practical because MCAS is frequently missed and honestly sometimes overdiagnosed. I start with the clinical picture. I'm looking for recurrent symptoms across 2 or more organ systems, the kind that flare and settle often with pretty identifiable triggers, and that also improve when we target mast cells. Then we look for objective evidence. Mast cell mediators are measurable. But they're delicate. So how you collect them matters. Serum tryptase is an important one. We check a baseline and ideally a level within a few hours of a flare, and we're looking for a rise of about 20% above baseline. That's the classic criteria. But here's an important caveat. In MCAS, tryptase is often normal. So a normal value doesn't rule it out. We also look at 24-hour urine mediators, something called N-methylhistamine, also prostaglandin D2. And also another cytokine or inflammatory molecule called leukotriene E4. Now, these are often telling us way more than the blood. There are other markers we can check, things like chromogranin A, plasma histamine, heparin. These are all medical things your doctor can check. They add a lot of information. Now, these samples are temperature sensitive and they must be kept chilled or you're going to get false negatives. And this trips up a lot of people in a lot of labs. So, Now here's where the functional medicine approach diverges from the conventional medical path. I don't stop here. You have MCAS, here's some antihistamines. I ask why these mast cells are activated. So the workup keeps going. Is it gut dysbiosis or SIBO, bacterial overgrowth? Is it mold or mycotoxin exposure? Is it chronic infections like Lyme or reactivated viruses? Is it low nutrient levels? Is it imbalance in hormones? Is it the state of your nervous system? Because MCAS is almost never root cause. It's like smoke. We want the fire. Now, a lot of foods fill the bucket. If histamine is part of your picture, food is one of the levers you can pull. In general, the longer food ages, ferments, cures, or sits, the more histamine it carries. The usual suspects are aged cheeses, wine, beer, champagne, fermented foods like sauerkraut, kimchi, kombucha, which— yogurt. Yeah, I know they're all healthy, but not for you. If you have a mast cell problem. Cured and smoked meats, fish, shellfish, vinegar, vinegary condiments. And here's what catches many people off guard. Many of these are, quote, health foods. Fermented foods are wonderful for most people, but healthy isn't healthy for everyone all the time. Context matters. You are going to hear a lot of conversations about detoxing this summer. The juice cleanses, the teas, anything promising to hit the reset button. But have you stopped to appreciate the detox system you already have? It's called your liver. Your liver processes every single thing you put into your system— the food, the alcohol, the medication, even the natural waste products. And it does this work every single day without a break, without applause. The challenge is that your liver works in silence, which means you might feel great while significant shifts are happening beneath the surface. And that's why we pay attention to liver biomarkers like ALT, ALP, AST, and GGT. Now, these show how your liver is actually holding up long before symptoms appear. And that's the exact reason why we built Function. Function gives you access to 160+ lab tests annually that measure signals in your blood, including nutrients, liver health, inflammation, and hormones. You can also complete your health baseline with an annual MRI that helps you see organs, tissues, and other changes. Check your health at functionhealth.com/marc. And if you're one of the first 1,000 people this week, use the code MARC2026 for a $50 credit for your $365 a year membership. A second group of foods doesn't contain much histamine, but can trigger its release in sensitive people. Tomatoes, spinach, eggplant, avocados, citrus, strawberries, chocolate. I know spinach and avocados, but this isn't about fear. These are nutritious foods. The point is simply that when your bucket is full, they can add to the load. And also freshness matters more than people expect. Histamine climbs as protein-rich food ages, even refrigerated. So No leftovers, right? Because bacteria produce it over time. Now, patients tell me all the time that they feel great eating freshly cooked salmon and terrible eating leftovers the next day. Same meal, different histamine. So to be clear, most people do not need a low histamine diet. We use it as a short-term investigation, not a life sentence. So how do we treat MCAS? Well, treatment is where functional medicine shines because we layer strategies rather than reaching for a single pill. Like an antihistamine. Think of it as calming the cells, clearing histamine, and healing the terrain all at the same time. So calming the cells, we get rid of the histamine and we heal the terrain, your whole biological terrain. You lower the load, low histamine diet trial, fresh foods, remove obvious triggers, gives the system room to settle. This buys us time while we work upstream. We use natural mast cell stabilizers and antihistamines. And this is often where I start, cuz there's a lot of great natural products that do this. Uh, they're gentle. They address the biology directly. One of my favorite is quercetin. It's a flavonoid, one of the best studied natural mast cell stabilizers. It works great for allergies. I use it all the time. It's also a longevity compound. It pairs well with bromelain for absorption. Also, there's another compound that's another flavonoid called luteolin, which is combined with quercetin, which has particular problems for brain fog and neuroinflammation. Vitamin C is a natural antihistamine that helps the body break down histamine. It also supports an important enzyme called DAO. You can also take DAO as a supplement. DAO is diamine oxidase. It's an enzyme that degrades histamine in the gut. You take it before meals when food-derived histamine might be a problem. There's also other herbs like stinging nettle, perilla, black cumin, which is also known as nigella sativa. These are botanicals with antihistamine and mast cell calming activity. There's also a lot of cofactors that are important for histamine breakdown. So all the enzymes like B6 as P5P, it's a pyridoxal 5-phosphate, a special form of B6, copper, which helps feed the enzyme, the DAO enzyme. They called SAMe and methylation support, which supports another pathway called the HNMT pathway that clears histamine inside your cells. Magnesium and curcumin also help to lower the broader inflammatory levels in your body. Probiotics also important. Make sure you choose them carefully. Some lactobacillus strains naturally produce histamine, so be careful. I lean toward histamine neutral or histamine degrading strains of probiotics like Bifidobacterium species, something called Lactobacillus rhamnosus and plantarum. Medications sometimes needed when we need more help. These are the conventional medical backbone, but they're often genuinely helpful. There's one called an H1 histamine blocker called sertraline, loratadine, fexofenadine, or ketotifen, which doubles as a mast cell stabilizer. There's also H2, which H1 is H1 histamine, H2 histamines. H2 histamines, typically they're thought of as stomach acid blockers, but they really work well as well, like famotidine for the gut. And also histamine receptors. And one of my favorites is a mast cell stabilizer called cromolyn sodium. It is used for gut-dominant symptoms and is given as a liquid called Gastrochrome 15 minutes before meals. And it really helps with histamine reactions. There's much more aggressive drugs like leukotriene blockers, like Montelukast, or the leukotriene-drawn piece. Also, you can use low-dose naltrexone or LDN, which is increasingly used to modulate immune and mast cell activity. Many of my patients do really well on it. Now, in severe refractory cases that nothing else works, you need anti-IgE therapies such as Omalizumab, which is a very heavy-duty drug. And the art is not starting with that. It's layering in these H1-2 blockers with stabilizers, natural agents, and then seeing how the person's doing, adjusting. Calming the nervous system is also really important. This is the piece that conventional medicine misses almost entirely. Mast cells are wired directly to the nerves and a dysregulated danger-sensing nervous system keeps them firing. Vagal toning, breathwork, limbic retraining, and trauma work aren't really just soft add-ons here. They're mechanistic in how they work. I've watched patients plateau on every supplement and medication until they've addressed the nervous system. Only then they turn the corner. Next, we want to fix the terrain, not just deal with mast cell inhibitors and nervous system regulation, which is important, removing the foods, all that's key. You've got to fix your basic biological health, your system. We call this fixing the terrain. And we treat what's actually driving the activation. Gut issues, we want to treat SIBO or bacterial overgrowth, dysbiosis. We want to get rid of mold if that's in your environment, in your system. We want to treat hidden infections like tick infections. We want to balance your hormones, make sure all your nutrients are optimized, get rid of toxins from your system, all super important. This is the part that makes everything else durable and work. Now, this next part is going to sound a little weird, but there's actually some good data on it. And it's called Helmintherapy. Now, historically, I'll explain why, but historically, you know, a body had to deal with worms and parasites. And there's a part of our immune system that releases mast cells that was really focused on that. Now it's kind of got nothing to do, so it's reacting to everything like foods that it shouldn't. And this is a bit of a provocative conversation, but some of the most treatment-resistant immune conditions including these overactive MCAS-type responses, trace back to an immune system that never learned to regulate itself. And this is called the Old Friends Hypothesis, which is the deeper cousin of the Hygiene Hypothesis. For all of human history, our immune systems co-evolved with parasites, particularly helminths or worms. We grew up alongside them. Our immune system regulation was calibrated by them. Then we got very clean, very fast, called sanitation. And then what happened? Well, allergy, autoimmunity, immune dysregulation just went through the roof. Helminth therapy is basically a deliberate controlled introduction of these organisms. And there's lots of different kinds of helminth therapies. There's hookworms, there's pig whipworms, there's rat tapeworms. They're, they're kind of still in a research phase, but they can be very helpful to recalibrate the immune system. Now, mechanistically, these helminths nudge the immune system toward a regulatory state. They expand what they call regulatory T cells. They raise anti-inflammatory signals. Interleukin-10 and TGF, or transforming growth factor beta. They quiet these inflammatory pathways that drive allergy and that drive these abnormal mast cell behavior. The research is developed mostly in inflammatory bowel disease, allergic rhinitis, and other autoimmune conditions with some intriguing signals. And for MCAS specifically, evidence is still largely theoretical, anecdotal. I want to be honest about that. It's experimental, isn't for everyone. It should only ever be done under knowledgeable guidance, but it points at something profound. Sometimes the answer isn't adding another medication. It's restoring a relationship our biology was built to have. That idea that we are ecosystems, not machines, is at the heart of how I think about all of this. The bigger picture is this. If you take one thing from today, let it be this: histamine and mast cells aren't the enemy. They're essential. The problem isn't that they exist. It's that in MCAS, the balance and the regulation have broken down. And our job isn't simply to suppress them forever. It's to ask why the bucket is overflowing and why the body has lost the ability to drain it. Is it the gut inflammation? Is it mold or infections? Is it hormones? Is it the nervous system? Is it immune system that never learned to stand down? When we answer those questions, we do something far more meaningful than managing symptoms. A low histamine diet, the supplements, the medications, they're useful tools, useful, sometimes essential tools, but they're the beginning of an investigation, not the destination. Because the goal of all this was never a restriction. The goal is resilience. Immune system steady enough and a body flexible enough that your diet and your life can expand again instead of shrink. It's not about symptom management, it's about healing. If you love that last video, you're going to love the next one. Check it out here.