MCAS Flare: A Slow, Surprising, Very Loud Wake-Up Call That Fridges Are Not Your Friend

For about eight years, Mast Cell Activation Syndrome (MCAS) was something I lived with quietly. It was there, but it wasn’t overly dramatic. It behaved itself most of the time, it showed up in small ways, a rash on the tops of my feet if I was in sunlight too long (sometimes as little as 10 minutes), or a patchy reaction if I accidentally touched a cleaning product, or used a product my MCAS didn’t like. Scents were tricky, but manageable. It was all very… contained, mild and predictable.

Then this summer arrived.

A series of heatwaves have hit the UK during the Summer. The kinds that make the air feel thick and your skin feel too tight and uncomfortable. The kind where you don’t want to cook because the kitchen already feels like a sauna. So we adapted, as you do. We ate salads, lots of raw vegetables, stored in the fridge because everything was going off far too quickly in the heat. We bought pre‑cooked meats and kept them chilled because who wants to stand over a hot cooker when the house is already melting?

It felt sensible and practical given the circumstances, and  a normal response to ridiculous weather.

But MCAS has its own logic. After months of this, months of delicious cold salads, fridge‑stored meats, and heatwave adapted-living,  my body suddenly shouted STOP. Not politely or gently. It did so loudly, dramatically, and unmistakably.

Here’s why fridges are not the friend of those of us with MCAS – it took me ages to get my head around this!

Most people can store food in the fridge for a few days without any issues. The food is still “safe”, it’s not off, it’s not spoiled, and it won’t make them sick. But MCAS works differently.

Even when food is fresh and perfectly safe, tiny amounts of bacteria start to grow as soon as it’s cooked or chopped. This is normal, it happens long before food smells bad or looks off. The fridge slows this process down, but it doesn’t stop it completely.

As bacteria slowly build up, they create histamine. The histamine keeps increasing the longer the food sits there.

So while a fridge keeps food safe for most people, it quietly turns food into something higher in histamine, which is exactly what MCAS reacts to.

That’s why my beloved salad, pre‑cooked meats, or veg chopped days ago can trigger symptoms even though they’re technically “fresh enough” and totally safe for everyone else. MCAS bodies aren’t reacting to spoiled food, they’re reacting to the histamine that builds up long before spoilage happens.

For MCAS, freshness isn’t about safety. It’s about keeping histamine as low as possible

When mast cells get upset, they release histamine. Histamine is one of the main chemicals that causes MCAS symptoms, inside and outside the body. Antihistamines help calm those reactions down.

There are two main types:

H1 antihistamines These calm the “outside” reactions. Things like itching, rashes, hives, skin flushing, and some allergy‑type symptoms. They help when your skin is shouting.

H2 antihistamines These calm the “inside” reactions. They work on the stomach and gut, helping with acid, nausea, cramps, and some internal MCAS symptoms. They help when your digestive system is shouting.

Most people with MCAS need both, because MCAS doesn’t just affect one part of the body, it affects everything.

Antihistamines don’t cure MCAS, but they help calm the mast cells down so your body can settle. They’re often used daily, and they become especially important during a flare, when mast cells are releasing far more histamine than usual.

During a flare, some people, under medical guidance, temporarily increase their antihistamines to help calm things down. My GP told me I could increase mine during this flare, and I’ve done that. If anyone else is dealing with similar symptoms, please speak to a healthcare professional before changing anything, because MCAS symptoms can overlap with other conditions. But in general, antihistamines are one of the few tools we have that can make MCAS feel less overwhelming. They help take the edge off the chaos inside the body and give you a bit of breathing room while you figure out your triggers, your food, and your next steps.

My current flare started with diarrhoea, six days of it. Six days of painful stomach cramps that made me curl up and breathe slowly. I cut out a few foods straight away, but nothing changed (like it had done during mild food-related flares previously) I didn’t feel better. If anything, I felt like my whole digestive system had gone on strike. Then came the lack of movement, slow bowel motility, stubborn, and still hanging around seven days later. I feel full and in pain after a few bites.  Like my stomach has forgotten how to move. My skin tingles with pins and needles, and occasionally, a sharp stabbing pain shoots through my duodenum, just to keep things interesting.

Through all of this, I knew this was caused by MCAS.  Not in a diagnostic sense, that’s for doctors, but in the lived‑experience sense. The pattern, timing, triggers, the way my body behaves when mast cells are unhappy, it all lined up.

So I found myself on a steep learning curve again. Or maybe I’d forgotten some of it, who knows? Brain fog is annoying like that.

I realised I’d been eating high‑histamine foods for months without meaning to. Not the foods themselves, but the storage. Raw vegetables sitting in the fridge for days. Pre‑cooked meats stored cold instead of frozen. All perfectly normal for most people, but for MCAS, it’s like slowly filling a bucket until it spills over.

Boy, oh, boy, spill over it did.

My biggest dilemma now is calories. How do you get enough energy when the foods that pack the most calories aren’t always MCAS‑friendly?

So far, I’ve been living on a medley of brown rice, eggs, chicken breast cooked from frozen, gluten‑free pasta, peeled cucumber, peeled carrots, and sweet potatoes. Though even sweet potatoes and egg whites come with warnings, they can be a problematic for some people with MCAS either full stop or when eaten in excess.

It’s a balancing act. A guessing game. A “Google is my friend” kind of situation. I look up every single food before I eat it. Every ingredient and cooking method. Every storage question. It’s slow, but it’s manageable. I personally find online forums and support groups overwhelming and too information-full, though I would recommend others tap into these free resources found easily online.

The dynamic at home is supportive, but also a little bit, “This had better not cost us too much money.” So I’ve been adapting to whatever we already had in the house since the last weekly shop. Making do and being creative in trying not to waste anything. But now I need to write a proper shopping list for next week, and honestly… it’s going to be epic.

Long‑term Foggy Followers will know I’ve been gently trying to lose weight for the past eleven months. I lost a stone in six weeks early on, less food, less food noise, and then I plateaued for nine months. I assumed it was perimenopause being its usual irritating self. Everyone around me seemed to be going through the same thing.

But now, looking back, I’m pretty sure MCAS was part of the picture too. 

During this flare, I’ve unintentionally lost six pounds. It’ll probably go back on once I’m eating normally again. But for now, it’s a strange relief not to feel bloated everywhere, ‘just’ in my stomach! A small silver lining in a very uncomfortable cloud.

When you live with M.E, your energy system is already fragile. Hypermobility adds instability to your connective tissue. MCAS? It reacts to both. It reacts to everything. It’s like having three sibling conditions that poke each other constantly.

One flares, the others join in. One calms down, the others follow. It’s a delicate ecosystem, and it doesn’t take much to throw it off balance.

I’ve noticed my joints, unusually including my wrists and ribs, have been particularly painful and creaky this week, I Googled…..ahh that’s why!!

People living with multiple chronic illnesses alongside MCAS learn, slowly, gently, and sometimes painfully.

You learn that fridges aren’t your friend. You learn that freezing food immediately can make a huge difference. You learn that slow cooking can increase histamine. You learn that browning food can be a trigger. You learn that your body isn’t weak , it’s protective. Just a bit too protective.

I’ve learned to take each day as it comes.

Right now, I’m still in the middle of it.  Still figuring out what I can eat without upsetting my mast cells. Still Googling every ingredient. Still adapting meals to whatever we already have. Still trying to keep the peace inside my body.

It’s not fun or easy. But it’s real, and it’s happening to me, and many others, right now.

If you’re walking a similar path, whether your MCAS is mild, moderate, or dramatic, you’re not alone. We’re all learning together, one cautious meal at a time.

So now I’m at the point where I need to write a shopping list. A proper one. Not the usual “what we always eat plus a few things that we fancy this week” list, but a “my mast cells are having a meltdown and I need to calm them down” list. Honestly? It feels like planning an expedition. But here’s what I’m starting with, foods that are generally lower in histamine when they’re fresh and that fit into my current “keep my stomach and mast cells calm, keep me fed” phase.

Another thing I have struggled with is remembering to consider the manufacture/processing of the food item. How long has this food item been around collecting histamines? I’ll never know internal processes but if it’s something I have bought pre-packaged/chopped from a supermarket the answer is likely – this is not MCAS friendly.