Mould, Breathing & Connecting the Dots

I’ve been a little quiet on social media and newsletters lately, and I wanted to share why.

Over the past few months, I’ve been deep down the rabbit hole of researching and connecting the dots between histamine intolerance (HIT), mast cell activation syndrome (MCAS), and a persistent health issue I’ve been managing, which, as it turns out, is linked to mould exposure in my own home.

After years of not feeling 100%, we recently discovered a hidden mould issue in my bedroom, stemming from a long-term leak that was never properly fixed by the developer after our home was built. This finding opened the floodgates to understanding how environmental factors like mould might be influencing my health on a deeper level.

Here’s what I’ve learned:

Mould & Mast Cells: A Hidden Connection

Mould spores are everywhere, especially in humid environments. These tiny particles can enter the lungs and trigger a powerful immune response, particularly from mast cells — the immune sentinels that live in our skin, lungs, and digestive tract.

When activated by mould, these cells release:

• Histamine (which causes inflammation, itching, congestion, and more) 

• Cytokines and proteases (which promote ongoing inflammation) 

• Prostaglandins (like PGD2, which are involved in allergy and asthma-like reactions) 

This immune cascade can lead to respiratory issues, fatigue, brain fog, nausea, and other hypersensitivity symptoms.

Mould as a Trigger for Chemical Intolerance & MCAS

One area that stood out in the research is mould’s role in chemical intolerance (CI) — a condition where the body reacts to small exposures to substances like fragrances, cleaning agents, or even certain foods and medications.

Multiple studies now show that:

• Mould is a known initiator of chemical intolerance. 

• Over 60% of people diagnosed with MCAS also experience CI. 

• Both conditions involve over-reactive mast cells releasing too many inflammatory mediators, too often. 

This means it hard tolerating certain environments, smells, and even foods, meaning the body is under constant fire.

Histamine Intolerance & the Role of Mould

Histamine intolerance isn’t about producing too much histamine,  it’s about not being able to break it down efficiently (often due to low DAO enzyme activity).

Combine that with:

• Histamine-releasing foods 

• Gut microbes and even some moulds that produce histamine 

• Inflammatory responses from mould-triggered mast cells… 

…and you’ve got the perfect storm.

While mould doesn’t cause HIT directly, it adds to the histamine load, making it harder for sensitive individuals to maintain balance.

What This Means 

This has been an eye-opening journey that’s helping me make sense of so many symptoms I previously wrote off for years and kept pushing through. The intersection between mould, MCAS, and HIT is still being studied, but the links are compelling,  especially for those of us living in humid climates or in homes with known water damage.

I’ll be sharing more on how I’m navigating this and breathing practices to support nervous system regulation.

If you’ve been struggling with unexplained fatigue, allergies, food sensitivities, or breathing issues, it might be worth looking into the role your environment is playing — especially when mould is involved. This is something I cover in the 60 min breathing assessment which you can book below. 

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