This transcript is condensed and lightly edited for readability, and is limited to the clinical discussion. A section of the conversation covering pandemic policy and commentary on the origins of the virus falls outside the scope of this page and is not reproduced here; the full unedited conversation is in the audio and video above.

What the ACE2 receptor is, and why it's everywhere

00:00Becca: You cannot look at the body the same way as we did pre-Covid. If you've felt like your body has just been toxic or dysregulated since that time, or since you got it, hopefully this connects a lot of dots — because we want to talk about what it actually did inside the body. Not the respiratory-only version. What we're seeing in real time: the nervous system, the mast cell activation, the histamine issues, the circulatory issues.

03:11Liz: A lot of people are calling this long Covid, and yes, we can call it that. But I'd rather just call it life after Covid, because everyone's immune system is so different, and it depends where you were in your phase of life.

04:42Liz: First you need to understand something called the ACE2 doorway. Every cell in your body has proteins sitting on its surface that act like locks. Some of those locks are meant to let specific things in — nutrients, signaling molecules, hormones. One of those locks is ACE2, angiotensin-converting enzyme 2. SARS-CoV-2 has a protein sticking off its surface called the spike protein, and it's shaped almost like a key, specifically to fit that ACE2 lock.

06:50Liz: Here's the part that matters for everything else we're going to talk about. ACE2 is not just sitting on your lung cells. It's on the cells lining your blood vessels — the endothelium — the cells in your heart, your gut, your kidneys. And the piece most people have never heard: it's found on mast cells, and on tissue throughout the nervous system. ACE2's normal job is regulating blood pressure, fluid balance and inflammation throughout the entire body. So you're not just giving the virus a door into the cell. You're disrupting a system your blood vessels, your heart and your immune system all depend on to stay balanced.

08:38Becca: Mast cells, nervous system, blood vessels — they all connect back to the same doorway. Imagine every building in a city having a master key. A locksmith who wanted to cause chaos wouldn't need to target city hall. They'd just need that one key, and suddenly every building is vulnerable at once. That's why this virus was capable of producing symptoms that look like they belong to completely unrelated diagnoses in the same person, sometimes all at once.

What mast cells actually do — and what happens when they stay switched on

11:06Becca: Mast cells have some of the highest levels of ACE2 receptors on them. And mast cells are immune cells — first responders, stationed at every border of the body with the outside world. Your skin. The lining of your gut. Your airways, all of those mucosal levels. The walls of your blood vessels. They're packed full of little granules loaded with histamine, tryptase and various inflammatory cytokines.

11:51Becca: When mast cells get triggered, they degranulate — they dump all of that content at once. That's what an allergic reaction is. But now it's happening on a more systemic level. It's not in relation to one thing, it's in relation to many things. You're not anaphylactic, but people will say: I'm getting hives on my hand, I'm flushing from exercise, I'm having headaches all the time when I never used to have them.

12:31Becca: In most of these cases the immune system has gotten so confused and dysregulated that it's responding to things it shouldn't. Random foods. A slight temperature change. Mental and emotional stress. It's become trigger-happy because of how much it's been stimulated.

What the research shows about spike protein and mast cell activation

15:11Liz: Mast cells concentrate in exactly the same tissue that's rich in ACE2 — skin, gut lining, airways, blood vessels. They carry ACE2 on their surface, which means the spike protein may be able to bind and activate them directly, not just indirectly through downstream inflammation.

15:33Liz: A 2023 study found that recombinant SARS-CoV-2 spike protein on its own was enough to stimulate human mast cells to release tryptase and IL-1 beta, and that effect got stronger when another inflammatory signal, IL-33, was present alongside it. In plain terms: they put spike protein in contact with human mast cells in a lab and watched them dump their inflammatory contents.

16:25Liz: That binding kicks off an internal chain reaction inside the mast cell, which causes calcium to flood in, and that triggers the cell's transport system to physically move those granules to the surface and release them. When the researchers blocked the calcium signal, the degranulation stopped completely. So we're not hand-waving at a vague mechanism — we understand it step by step.

17:19Liz: And this wasn't only done in a lab. A study published in the Journal of Clinical Investigation looked at actual Covid patients and found mast cell activation in the lungs was directly tied to disease severity. Tryptase levels in the blood correlated with how sick people got, and with markers of vascular dysfunction. In an experiment using mice bred to lack mast cells entirely, those mice had dramatically less lung damage than normal mice — despite the exact same viral load. That begs the question: why do two people exposed to the same thing get totally different results?

17:43Liz: This is strong evidence that mast cells weren't just innocent bystanders reacting to the virus. They were actively driving tissue damage. Hello leaky gut. Hello cardiovascular issues, asthma, allergies, all of it.

Why mast cell activation diagnoses surged after 2021

18:18Liz: Hear me when I tell you, we have not seen the level of MCAS diagnosis ever before that we're seeing today, and this mechanism is why. A study out of the International Journal of Infectious Diseases looked at 136 long-Covid patients and compared their symptoms to 80 patients already formally diagnosed with mast cell activation syndrome. Before the Covid infection, the long-Covid group looked just like healthy individuals. After they developed long Covid, their symptom pattern and its severity became nearly identical to people with a formal MCAS diagnosis — fatigue, headaches, joint pain, muscle pain, cognitive issues, brain fog, neuropathy, sleep disturbance. The same picture as classic mast cell activation.

19:12Liz: I do want to pause and say this is a very real thing, but don't leave this podcast saying “Becca talked about this, so I have MCAS.” You have to have multiple tests. Headaches could be coming from many other things — GI issues, toxins crossing the blood-brain barrier, magnesium deficiency, B2 deficiency, hormonal fluctuations. But if you had sudden-onset racing heart, hives, flushing and anxiety you've never felt before, go back and look at the timeline.

20:23Liz: We ask in our intake forms: tell me about your experience with Covid. How severe was it? What happened in that time frame? What about the people around you? I want to use that as clinical data.

How estrogen and histamine make perimenopause worse

20:48Liz: A lot of the women we work with collided with Covid at the same time they collided with the shift of hormones in perimenopause. And because estrogen amplifies histamine, that made an already difficult transition much worse for many of them. Progesterone can help stabilize it. But you have to look at the other factors at play first, which is why we're so cautious about putting estrogen in before we've looked at everything else.

21:25Becca: Part of me thinks this is why perimenopause has been so hard for so many women over the past five or six years. Perimenopause was always a thing, but you see it so much more now because of how awful people feel during it — and I think a lot of that is this.

21:47Becca: Histamine doesn't just cause one kind of symptom. Mast cells are stationed everywhere and histamine receptors are everywhere. It's in your skin — flushing and hives. It's in your gut — cramping, bloating, reflux, diarrhea. It's in your blood vessels — a drop in blood pressure, that lightheaded feeling. In your brain it acts like a stimulant, which is part of why so many people feel wired and anxious, like their thoughts are racing for no reason.

Four diagnoses, one overactive alarm system

22:25Becca: One trigger. One cell type. But symptoms are everywhere. They look like an anxiety disorder, a digestive disorder, a skin condition, a cardiovascular issue. The number of women who have gone and gotten full cardiovascular workups because they think something is wrong with their heart — and there's nothing wrong with the heart. But it's terrifying.

22:45Becca: That's four separate problems. One overactive alarm system. This is where mislabeling does real damage, because a woman will come in with hives and heart palpitations and gut symptoms, and depending on which doctor she sees first, she can walk away with a completely different diagnosis and four separate prescriptions — when none of them are actually fixing what's going on.

Racing heart, dizziness, and a nervous system with no off button

23:28Becca: The second major system caught in this crossfire is the autonomic nervous system — the part that runs on autopilot. Heart rate, blood pressure, digestion, temperature regulation, sweating. It has two main branches: sympathetic, your gas pedal, and parasympathetic, your brake pedal. The vagus nerve is the highway for that calming branch.

24:18Becca: The data on how many long-Covid patients have autonomic dysfunction is staggering. A large global survey of over 2,300 adults with long Covid, using a validated tool called COMPASS-31, found the majority had moderate to severe autonomic dysfunction. And the craziest detail: the severity of someone's original infection didn't predict it. People who had a mild infection could end up with significant, measurable autonomic dysfunction afterward.

24:46Becca: In patients referred for formal autonomic testing, a high proportion met the full diagnostic criteria for POTS — postural orthostatic tachycardia syndrome. That's a heart rate increase of 30 beats per minute or more just from standing up. Your blood flow can't keep up with your movement, so you spike adrenaline, and that causes the anxiousness, the lightheadedness, the dizziness, the rapid heartbeat.

25:33Becca: Not every study agrees on exactly how much shows up on standardized objective testing versus what patients report subjectively. But the pattern across study after study, using different methods in different populations, keeps landing the same way. This is very real, it's measurable, and it's becoming commonplace.

25:54Becca: It can feel like you stand up and your heart's racing, or you get lightheaded, or the floor is tilting. Like you need more salt and fluids than you ever did just to feel normal. Your temperature regulation goes haywire. Digestion becomes unpredictable, because the vagus nerve is a large contributor to motility — so people end up with bloating, constipation, SIBO. You feel tired and wired at the same time, like your nervous system cannot find an off button.

28:22Liz: And this goes both ways, because an unstable, dysregulated nervous system creates physiological stress, and that stress in itself further activates mast cells. High seasons of stress exacerbate all of it. One of our clients in maintenance was doing amazing, then had a death in the family and a move — and the symptoms came right back.

30:48Liz: You cannot out-supplement, out-peptide or out-hormone a lack of stress management and a diet that isn't giving your body the nutrients it needs.

Why standard bloodwork doesn't see any of this

33:25Becca: What's really hard about this is that bloodwork was never created to test the autonomic nervous system. It wasn't created to test mast cell activation. You can't really see those things very well in labs. You have to know what you're looking for, you have to know the patterns that appear and how people get triggered, and you have to know the health history — which is why we're so big on looking at the body as a whole.

34:07Becca: We ask weird questions and people say, why do you need to know that? Because you need to be able to decipher whether this is actually what's going on, or whether something is just mimicking it.

Covid as a vascular condition: endothelium, micro-clots and brain fog

34:25Becca: This is where the research has shifted most since 2020. Covid is increasingly described in the literature not as a respiratory disease but as a vascular one — a disease of the blood vessels. A 2020 paper in Cardiovascular Research put it clearly: the endothelial cells that line every blood vessel in your body, and the pericytes that wrap around and support the small capillaries, carry ACE2. So the lining of your blood vessels isn't collateral damage from a lung infection. It's a direct target.

34:46Becca: Your endothelium is a paper-thin lining doing a huge job. It controls clotting. It controls how tight or how leaky your vessels are. And it regulates blood pressure locally, vessel by vessel, throughout your entire body. When the virus damages that lining directly, you get capillary leakage — fluid, proteins and immune cells leaking out — disrupted oxygen exchange in tissues that have nothing to do with your lungs, and micro-thrombi, tiny clots forming throughout the small vessels.

36:23Becca: That elevated D-dimer marker is important. It's a direct readout of ongoing clotting activity happening somewhere in the body in real time. Under normal circumstances your body forms and dissolves microscopic clots constantly. But when D-dimer is persistently elevated, that tells you the body is working overtime on clot formation and breakdown at a scale beyond normal maintenance. And the frightening thing about clotting is you don't feel it happening.

36:44Becca: Clinically this shows up over time as cold hands and feet, exercise intolerance that doesn't make sense for someone's fitness level, brain fog that's honestly about poor micro-circulation to the brain rather than a neurological problem, unusual bruising, and fatigue that does not resolve with rest.

40:08Liz: We're also seeing higher levels of gastroparesis because of how this impacts the gut lining. Things slow down, and when things sit and ferment you get worse bloating and bacteria overgrowing, which further hijacks the immune system.

What actually calms mast cells down

41:36Liz: The truth is it's not sexy and it's not easy. We have to calm the mast cells down, and that's not going to be just taking a histamine supplement. It's root-cause work. It's changing your diet and removing the things that are triggers.

41:54Liz: You have to put out a fire. We've always talked about this from the gut, but now it's the whole body, because these mast cells live everywhere. You're a person walking down the street on fire. Who do you want in your corner — the person bringing water to put the fire out, or the person bringing fuel? We have to put the fire out first. Then clean up the debris. Then get you new clothes, because you're all burnt up. Then help with the restoration process.

42:57Becca: On the gut side, DAO taken 10 to 15 minutes before meals can be helpful, because your mucosa is where DAO is produced. In a lot of these cases the mucosal layer is depleted and has to be rebuilt — immunoglobulins can be very helpful there. Sometimes a high-quality aloe vera acts as a mild mast cell stabilizer. Sometimes we have to go heavier, including antihistamines for a short period, to get symptoms calm enough to work on the rest of the system.

43:56Becca: Then we re-nourish — vitamin C, vitamin E, bioflavonoids, liver support, selenium. Things that play a large role in immune function. Then the nervous system, which is less tactical: evaluating your stress, vagal toning, deep breathing, gargling, getting in person with a therapist, sound therapy. Really trying to stabilize a system that's been dysregulated for a long time. High doses of electrolytes, salt and water help here as well.

45:05Becca: Then the circulatory piece. And checking labs to see what's actually been affected — is this now also an iron issue, a metabolic issue, a gut issue? Because we need to be digesting and absorbing. Bile plays a large role as a main transport of toxins and hormones out of the body.

Why the fix has to be slow and individual

46:02Becca: I've seen three cases in the past month that ended up in the ER — numbness and tingling in the hands, anxiety, lightheadedness, dizziness, almost vertigo-type symptoms. Nothing wrong on labs, because it's an autonomic nervous system problem.

46:28Becca: The approach has to be slow. It has to be calculated. I need to know how someone is tolerating things and why something is happening. In a lot of cases it doesn't even make sense at first, and then you figure it out — because that's what good practitioners do. It is not black and white. It is not straightforward.

49:19Liz: And if you ignore the nervous system piece, it gets really challenging. I have a case right now with severe, debilitating anxiety, and we're seeing nutrient depletions across the board, because stress burns through your minerals, your B vitamins, your magnesium, your vitamin C, your potassium.

53:03Liz: Your symptoms are very real. They are not in your head. You are not crazy. But you do have to start working on the belief that you can heal, because that's the part we can't do for you.

Frequently asked questions

Why can't I tolerate dairy or fermented foods anymore?

Both are high-histamine. FitMom's practitioners see this constantly after a Covid infection: mast cells in the gut lining stay hyper-reactive and release histamine into a system that's already carrying a load, so foods you ate for forty years suddenly cause bloating, flushing or headaches. The food didn't change. The threshold did — your body now reacts at a level it used to absorb without noticing.

Why does my heart race when I stand up after having Covid?

That pattern points to autonomic dysfunction. Standing requires your nervous system to instantly redirect blood flow; when the autonomic branch that manages that is dysregulated, blood flow can't keep up and adrenaline spikes to compensate. The result is a racing heart, lightheadedness and a sense of panic with no emotional trigger. FitMom's practitioners assess this pattern directly rather than treating it as anxiety.

Why is my brain fog still here two years after Covid?

Becca Chilczenkowski's framing: much post-Covid brain fog is a circulation problem, not a neurological one. The lining of the small blood vessels carries ACE2 and can be damaged directly, which disrupts micro-circulation and oxygen delivery to brain tissue. That shows up alongside cold hands and feet, unexplained bruising, and exercise intolerance that makes no sense for your fitness level — a plumbing pattern, not a brain pattern.

Can Covid cause mast cell activation syndrome?

Published work has compared long-Covid patients against people with a formal mast cell activation diagnosis and found the symptom pictures nearly overlap — fatigue, headaches, joint and muscle pain, brain fog, neuropathy and disrupted sleep. Before infection, the long-Covid group resembled healthy controls. FitMom's practitioners treat that timeline as clinical data, though a real diagnosis requires multiple tests rather than symptom matching.

Why did my perimenopause symptoms get so much worse after Covid?

Estrogen amplifies histamine, and progesterone helps stabilize it. So a woman entering perimenopause at the same time her mast cells became reactive is running two histamine problems at once. Liz Roman and Becca Chilczenkowski see this collision constantly in women 40–55 — which is also why they're cautious about adding estrogen before the histamine and gut picture has been addressed.

Why do all my labs come back normal when I feel this bad?

Because standard bloodwork was never designed to measure either of the two systems most involved. Routine panels don't assess autonomic nervous system function, and they don't capture mast cell activation. Becca Chilczenkowski's point: you have to know the patterns, the triggers and the health history to see it. Normal labs mean the standard panel found nothing — not that nothing is wrong.

What is dysautonomia, and how is it related to long Covid?

Dysautonomia means your autonomic nervous system — the automatic branch running heart rate, blood pressure, digestion, temperature and sweating — isn't regulating properly. After a Covid infection, this shows up as heart rate spiking on standing, temperature regulation going haywire, needing far more salt and fluid than before, and digestion turning unpredictable. Long-Covid cohorts show measurable autonomic dysfunction at high rates, including in people whose original infection was mild.

Why do I get hives, flushing and headaches out of nowhere now?

Mast cells sit at every border between your body and the outside world — skin, gut lining, airways, blood-vessel walls — packed with histamine. When they become trigger-happy, they release it in response to things that were never threats: a food, a temperature change, emotional stress. Because histamine receptors are everywhere, one overactive cell type produces symptoms that look like four unrelated conditions.

Key terms

ACE2 (angiotensin-converting enzyme 2)

A surface protein SARS-CoV-2 binds to in order to enter cells. Normally part of the renin-angiotensin system, which regulates blood pressure, fluid and sodium balance, and inflammation.

Spike protein

The structure on the virus surface shaped to fit the ACE2 receptor, like a key into a lock.

Mast cell

An immune first-responder stationed in skin, gut lining, airways and blood-vessel walls, loaded with granules of histamine and inflammatory mediators.

Degranulation

When a mast cell dumps its entire granule contents at once. The mechanism behind an allergic reaction.

MCAS (mast cell activation syndrome)

A condition where mast cells release mediators inappropriately, producing symptoms across multiple body systems at once.

Histamine

A signaling molecule released by mast cells. Causes flushing and hives in skin, cramping and reflux in the gut, blood-pressure changes in vessels, and acts as a stimulant in the brain.

DAO (diamine oxidase)

The enzyme that breaks down histamine from food, produced largely in the gut mucosa.

Autonomic nervous system

The automatic branch controlling heart rate, blood pressure, digestion, temperature and sweating. Sympathetic is the accelerator; parasympathetic, via the vagus nerve, is the brake.

POTS (postural orthostatic tachycardia syndrome)

A heart rate increase of 30 bpm or more on standing, with associated dizziness and adrenaline symptoms.

Endothelium

The single-cell-thick lining of every blood vessel. Controls clotting, vessel permeability and local blood pressure.

D-dimer

A blood marker of active clot formation and breakdown. Persistent elevation indicates clotting activity beyond normal maintenance.

Gastroparesis

Delayed stomach emptying, which drives bloating and bacterial overgrowth downstream.

Studies and sources referenced in this episode

• Nature Communications (2020) — receptor-binding domain / ACE2 interaction mapped at molecular level
• Nature Reviews Molecular Cell Biology — SARS-CoV-2 cell entry process
• Journal of Clinical Investigation — mast cell activation in lungs correlated with Covid severity
• International Journal of Infectious Diseases — 136 long-Covid patients compared with 80 patients formally diagnosed with mast cell activation syndrome
• Journal of Virology (2025) — spike–receptor binding across the coronavirus family
• Cardiovascular Research (2020) — endothelial cells and pericytes carry ACE2
• COMPASS-31 survey of autonomic symptoms in long Covid (approx. 2,300 adults)

The Health Revival Show is educational and is not medical advice, diagnosis or treatment. Mast cell activation syndrome, POTS and dysautonomia are clinical diagnoses that require evaluation and testing by a qualified provider. Speak with your own clinician before changing medication, supplementation or diet.