You Can Eat Very Healthy - But It May Not Be the Right Diet for You: How Histamine Intolerance & Mast Cell Activation Play a Role

mariekesteen
17 minutes ago
4 min read

When a “clean” diet still triggers symptoms

I just spent the past couple of weeks in Vietnam and something unexpected happened.

I travelled to Vietnam, fully expecting my skin and histamine symptoms to worsen. Between airplane travel, traffic, scooters, visible air pollution, heat, humidity, and unfamiliar foods, it seemed like the perfect storm. Instead, my skin calmed down almost as soon as we arrived. The persistent eye irritation disappeared. The background inflammation I had been trying to regulate for months simply… eased.

Nothing dramatic changed.

I still ate (fairly) well (although no organic foods available, vegetable cooking oils and lots of sugary sauces that one couldn’t avoid). I still supported my nervous system. I still prioritised sleep.

But something fundamental was different - and it made me realise something I see all the time in my clients:

You can eat very healthy, and still be eating in a way that is not right for your biology.

A quick recap: air pollution, histamine intolerance & mast cell activation

In my previous article, I shared how air pollution and environmental exposure can activate mast cells, leading to symptoms that look like allergies but aren’t classic allergies at all.

Things like:

teary, swollen eyes
skin irritation or rashes
a constantly “full” histamine bucket
reactions that appear random or seasonal

For many women - especially in perimenopause - fluctuating estrogen levels already make mast cells more reactive and low progesterone hinders histamine breakdown. Add pollution, stress, and immune load, and your bucket flows over.

What I hadn’t fully appreciated until Vietnam was how much my diet was quietly adding fuel to that fire.

What changed in Vietnam (without trying)

Looking back, several things shifted naturally:

I ate freshly cooked meals prepared just before eating
I rarely ate leftovers
Protein sources were simpler and fresher
Meals were lighter, less repetitive
I unintentionally reduced foods that increase histamine load over time

Importantly, I wasn’t eating “better” - I was eating differently

At home, my diet is objectively very clean:

lots of vegetables
legumes, seed bread, fermented flavours
meal prep for efficiency
leftovers & canned fish to save time
ACV in the morning on waking

But here’s the key insight: A diet can be anti-inflammatory on paper and still overload histamine and mast cells in real life.

It’s not just histamine – it’s mast cell activation

This is where many people get stuck.

They remove high-histamine foods… but symptoms persist.

Why?

Because histamine intolerance and mast cell activation are related but not the same.

Histamine intolerance is about:

how much histamine you consume
how well you break it down (DAO, HNMT)

Mast cell activation is about: how easily your immune system releases* histamine and other mediators

how reactive your system is overall

In my case:

I don’t have a DAO SNP
I DO have slower HNMT activity
I live in a high-pollution environment
I’m in a hormonally sensitive life stage

So even foods that are traditionally considered “healthy” - leftovers, slow-cooked meals, certain vegetables, repeated proteins - were filling my bucket without me realising it.

Why women in perimenopause are especially vulnerable

Estrogen directly influences mast cells and progesterone impacts histamine clearance.

As hormones fluctuate:

mast cells become more reactive
histamine clearance becomes less predictable
the margin for error shrinks

This is why many women tell me:

“I’ve eaten like this for years - why is it suddenly not working?”

The answer is rarely willpower or discipline.

It’s physiology changing.

What I didn’t fully appreciate at the time was that histamine wasn’t acting alone. The missing piece was my nervous system. Chronic stressors - including past mold exposure, persistent low-grade infections, hormonal shifts, and ongoing environmental pressure like air pollution - can all reduce vagal tone, the nervous system’s ability to “switch off” inflammation. When vagal tone is low, mast cells are more easily triggered and much slower to calm down. This means that even foods or exposures I had tolerated for years suddenly pushed my system over the edge. The issue wasn’t that I was doing the wrong things - it was that my body had lost some of its regulatory capacity. Once I understood this, everything made sense: why symptoms lingered after exposure, why my eyes stayed swollen even indoors, and why eating very “clean” still wasn’t enough. It wasn’t about removing one more trigger - it was about restoring the body’s ability to shut the response down.

The takeaway: personalize, don’t restrict

The solution isn’t fear of food.

It’s understanding:

your total histamine load
your mast cell threshold
how environment, hormones, stress and food stack together

Sometimes the most supportive change isn’t what you eat - but:

how fresh it is
how often it’s repeated
how long it’s stored
how stimulating it is for your nervous and immune system

Want to go deeper?

I’ll be teaching this in detail in my new masterclass where we’ll cover:

histamine vs mast cell activation (and why it matters)
why “healthy” diets can backfire
the role of air pollution, hormones and nervous system tone
practical strategies to lower your histamine load without living in the kitchen