Food Fear is Real
Food fear is real.
There is nothing quite like being a foodie, the obsessed, travel-to-the-ends-of-the-earth-for-one-great-meal type of foodie, only to be hit with MCAS, Mast Cell Activation Syndrome. In a simple phrase: it sucks.
Mast cells are your immune system’s smoke detectors. We need them to do their job. They sit in the tissue that touches the outside world: skin, gut, sinuses, lungs. When they detect a real threat, they burst open and release a cascade of mediators that calls in the rest of the immune system. Histamine is the most famous chemical in that cascade, but there are hundreds.
MCAS is what happens when those detectors stop discriminating. Mast cells are supposed to fire at real invaders. In MCAS they fire at dinner. Which is why a plate of aged cheese can read like anaphylaxis.
I remember dining at Tom Kitchin’s fantastic The Kitchin in Leith, Edinburgh. I had dined there a week earlier and decided to return one more time before I left the area. This time I opted in for the cheese course. I had no reactions at all the last few times I dined there. I adored the iconic hand-dived Orkney scallops baked in the shell, which tasted sweet and gently salty, so very fresh from the sea. I ate to my heart’s content and my full belly’s disgruntlement. But the cheese course got me. As I sat at the lovely window table, something began to shift. As I left to walk back to my flat I felt a real heaviness coming on, the cobbled path uneven and sloping, precarious in an unusual way. As I walked along the canal actually the Water Of Leith river, in the (rare) sunlight, past the swans with their eight furry cygnets scooting behind them, I didn’t stop as I usually did. A visit to them was a daily ritual, but today I was dropping into something, something that gave me tunnel vision to return to my nest. I couldn’t enjoy my walk or the place that I so love. It was difficult climbing the stairs to my fourth floor apartment, a rooftop I shared with the boisterous seagulls. I felt thick, like I was wading through mud. I was anxious and felt compelled to lie down. I did, and slept for three hours, only to awaken craving Pellegrino and something sweet. The typical aftermath. I went down to the nearest pub for a liter of the bubbly elixir that rights my ship.
Others get skin reactions, throat closures, headaches, brain fog, pain. It can be very serious in a variety of ways. I had experienced something similar after a Thanksgiving meal and a Christmas banquet, but this was the first time it hit that hard, and the first time it happened somewhere I couldn’t retreat from quickly.
Over time, with each new assault on my system, living in mold, that pesky virus, living in mold again, and an antibiotic called Cephalexin were the big final straw. Nearly anything I ate or ingested as a supplement caused a crash daily. I became determined to figure this out and help others too. But for a time, food was terrifying.
Blueberries blended with heavy cream became my safe sanity food when MCAS limited what I could eat to chicken, rice, butter, and olive oil. That addition to my safe list became part of my mental health medicine.
Food fear is real and it is AWFUL. I remember a night, after I’d had a bad run with severe reactions and had not ventured off the safe list for quite some time, I attempted to feel like a normal girl and went out for dinner with a friend. As I stood at the counter looking at options, reviewing the ingredients for each choice, I became overwhelmed and started to have an anxiety attack. Tears welled up in my eyes. I apologized to the gal behind the counter and my friend over and over for being difficult and “ruining” the evening.
Thank goodness I was with a wonderful friend who held the space, didn’t get upset, and tried to think of alternatives including a raincheck.
Ultimately, as I calmed, we went elsewhere and I ate something quite clean, after torturing our server with a million questions for which she so politely found the answers.
I am finding some patience for my needs out in the dining world, which makes getting back out there more inviting and safer. But it feels terrible, I’m sure it is annoying.
Thank you to all of the people who hold space for food sensitivities, for the dangers of MCAS, for the complexity of navigating this strange and vulnerable situation we deal with. I couldn’t do this without the support of these people, a few friends who may not get it but don’t hold it against me or judge it, and a community of others navigating this.
P.S. I can't wait to return to The Kitchin. It's one of the few restaurants I go back to again and again, and have since 2012. I live in the US. It is that worth it. None of this is a knock on The Kitchin. My mast cells simply had opinions about aged cheese that night. I'll be armed with my MCAS kit should things rear up, but I'm fairly certain it's under control now.
Understanding Mast Cell Activation Syndrome
A starting guide for people who have MCAS, or suspect it, - Pamela Dobbie
What Your Mast Cells Are Doing
Mast cells sit in your tissues — skin, gut lining, airways, blood vessels — as part of your immune system's first response team. When they detect a threat, they release chemical mediators: histamine, tryptase, prostaglandins, leukotrienes, and others. In MCAS, mast cells release these mediators too easily, too often, or in response to things that shouldn't trigger a response at all. The result is a pattern of symptoms across multiple systems — flushing, hives, GI upset, headaches, rapid heart rate, brain fog, and sensitivities to foods, smells, temperature, and exertion — that often shifts from day to day.
A useful way to think about it: your body carries a total mediator load, sometimes called the “histamine bucket.” Every trigger adds to the bucket, and symptoms show up once the bucket overflows — not necessarily from any single trigger alone. That's why the same food can be fine on one day and provoke symptoms on another: it's the total load, not one ingredient in isolation.
Common Aggravators
High-histamine foods: aged cheese, cured or processed meats, fermented foods (sauerkraut, kombucha, vinegar), wine and other alcohol, and leftovers — histamine climbs the longer food sits.
Histamine-liberating foods: citrus, tomatoes, spinach, strawberries, chocolate, shellfish — these push existing mast cells to release histamine even though the food itself isn't high in histamine.
MSG (monosodium glutamate): acts directly on mast cells and can trigger degranulation independent of a food's histamine content.
MCT oil: a common “gut-healing” supplement that acts as a mast cell degranulator in some sensitive people. If it's in your coffee, shakes, or capsules and a symptom pattern doesn't add up, it's worth removing as a test.
DAO-blocking substances: alcohol, energy drinks, and several medication classes (NSAIDs, some antibiotics, some antidepressants) reduce the enzyme that clears dietary histamine.
Environmental triggers: mold and mycotoxin exposure, fragrances, extreme heat or cold, and exercise.
Nervous system load: mast cells are directly innervated by autonomic nerve fibers, so a chronically activated nervous system can lower the threshold at which they fire.
Hormonal shifts: estrogen increases mast cell reactivity and decreases DAO activity, which is why symptoms often track the menstrual cycle.
The Leaky Gut Connection
About 70% of the body's mast cells live in the gut lining — positioned right at the border between what's inside you and what's still technically outside. That border is held together by tight junctions between intestinal cells. When those junctions loosen (“leaky gut,” or increased intestinal permeability), partially digested food proteins, bacterial fragments, and other material cross into gut tissue where mast cells and immune cells sit waiting. That crossing is itself a trigger.
The relationship runs both directions. Mast cell mediators like histamine and tryptase can further loosen tight junctions, so a permeable gut feeds mast cell activation, and mast cell activation feeds gut permeability. Addressing gut barrier integrity is usually central to lowering the total mediator load — not a side project.
Testing That Can Show Leaky Gut
Zonulin — blood or stool — measures the protein that regulates tight junction opening; elevated levels indicate increased permeability.
Lactulose/mannitol test — two inert sugar molecules of different sizes are ingested, then measured in urine. Mannitol should pass through easily; lactulose shouldn't. A higher-than-expected lactulose-to-mannitol ratio means the gut lining is letting through what it shouldn't.
LPS antibody testing — measures immune reaction to bacterial fragments that leak through a permeable gut.
Comprehensive stool testing — e.g. GI-MAP — shows dysbiosis, inflammation markers like calprotectin, and secretory IgA, the gut's frontline antibody, where both very low and very high levels can point to a barrier under strain.
Cyrex Array 2 — an intestinal permeability panel that looks at antibodies to the barrier proteins themselves.
None of these need to be run all at once — work with a provider who can help sequence testing to your history and budget.
Supplements That Can Help With Eating
These work by lowering the mediator load around meals, not by treating MCAS as a whole.
DAO (diamine oxidase) — the enzyme your gut normally produces to break down histamine from food before it enters the bloodstream. Taken shortly before a meal, supplemental DAO gives you more capacity to clear dietary histamine.
Perilla (Perilla frutescens seed extract) — contains rosmarinic acid and luteolin, compounds studied for stabilizing mast cell membranes so they're less quick to degranulate.
Quercetin — a flavonoid that stabilizes mast cell membranes and blocks histamine release at the source. It requires gut bacteria to cleave its sugar molecule before it can absorb — which matters if your gut flora is already compromised.
Isoquercetin — a more bioavailable form of quercetin. The sugar is attached differently, so it doesn't need bacterial conversion to absorb — often the better choice when dysbiosis is part of the picture, since it doesn't depend on gut function that's already under strain.
Work with a provider on dosing and sequencing — individual response and tolerance vary, and some of these interact with medications.
Why DAO Might Be Low
DAO is produced by the cells lining your small intestine, so anything that damages that lining lowers your own production — this is the direct link back to leaky gut. Other contributors:
Genetic variation in the AOC1 gene, which affects how much DAO you produce regardless of gut health.
Gut inflammation or dysbiosis, including SIBO, reducing the health of the DAO-producing cells.
Alcohol, which directly inhibits DAO activity.
Certain medications: NSAIDs, some antibiotics, some antidepressants, some diuretics.
Nutrient status: DAO production depends on vitamin B6, copper, and vitamin C as cofactors, so deficiencies in any of these can lower output even with a healthy gut lining.
Other Factors Worth Knowing
Mold and mycotoxin exposure is one of the more overlooked mast cell triggers. If symptoms started or worsened after a water-damaged building exposure, that history is worth investigating directly — not just treating what shows up downstream.
A low-histamine diet is a short-term diagnostic and stabilizing tool, not meant to be permanent. The goal is to lower the bucket enough to identify individual triggers, then reintroduce as tolerated.
H1/H2 antihistamines and mast cell stabilizers (like cromolyn) are prescription tools some people need alongside diet and supplement changes — that's a conversation for a prescribing provider, not something to self-titrate.
A trigger/symptom log kept for a few weeks (food, environment, stress, cycle timing, symptom onset) usually reveals patterns faster than eliminating everything at once.
Next Step
Work with a provider who understands the gut–immune–nervous system relationship in MCAS, and be specific about your exposure history — mold, infections, major stressors — since that history often explains why symptoms started when they did.
For Information on Lab testing and the professional grade supplements I prefer check them out here on my Fullscript Dispensary.
To learn about the method I used and use with clients for help with Mold Illness Click HERE
This handout is educational and not a substitute for individualized medical care.