Too Much Histamine Is Wrecking Your Body — And Most Doctors Don't Know It

**Dr. Mark Hyman** (0:01)
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 avocados, 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. It's called Mass 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 M-C-A-S, Mass Cell Activation Syndrome. Now, what we're going to cover is a lot. We're going to cover what mass cells actually do, why they sometimes go haywire. Mass 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 Hell-Ment 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 to that. So let's dive in. This episode was brought to you by Function. Get access to over 160 lab tests annually at functionhealth.com/mark. 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 three 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 protected. 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 live in every organ system, MCAS can look like almost anything. In your skin, it can be flushing, highs and itching, writing on your skin when you scratch it, called dermatography.
It can be in your gut, the 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. For many women, that explains symptoms long dismissed as just 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 a period around ovulation or unpredictable and 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 two or more organ systems, the kind that flare and settle often with pretty identifiable triggers, and then 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 triptase is an important one. We check a baseline and ideally a level within a few hours of a flare. We're looking for a rise of about 20% above baseline. That's a classic criteria.