... a condition where mast cells — an important part of your immune system — become overactive and release chemicals too easily, causing a wide range of symptoms across the body.
What are mast cells?
Mast cells are our immune system's first line of defence.
They are found in high numbers in our skin, our respiratory tract, our gut and our urinary system - any part of the body where the tissue is in contact with the wider environment is loaded with mast cells, ready to jump to action to provide protection.
Mast cells are also present in the nerves, in blood vessels, in lymph nodes, in the heart and in the meningeal lining of the brain.
What is Mast Cell Activation Syndrome (MCAS)?
When mast cells sense danger, they “activate”, releasing chemical messengers such as histamine, leukotrienes and prostaglandins. These chemicals help coordinate an immune response — but they can also cause a wide range of symptoms.
Common effects of mast cell activation include:
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allergy-type reactions (flushing, itching, hives, swelling)
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inflammation and pain (muscle, joint or nerve pain, headaches)
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digestive problems (nausea, diarrhoea, abdominal pain)
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bladder or pelvic pain
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fatigue and brain fog
When mast cells become overactive and too easily triggered, the result is Mast Cell Activation Syndrome (MCAS). Because mast cells are found all over the body, MCAS can cause symptoms in many different systems, often making it difficult to recognise.
✨ Do these symptoms sound familiar? Are you ready to explore your treatment options?
MCAS and mould illness
Mould and the biotoxins it produces are among the most potent triggers of mast cell activation. For sensitive individuals, even small exposures can keep mast cells on “high alert.”
This can result in a vicious cycle:
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Biotoxins activate mast cells
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Mast cells release more inflammatory chemicals
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These chemicals need to be detoxified, further burdening the body’s clearance systems
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Overloaded detox pathways → even more mast cell activation
For many patients, mould exposure is a hidden but critical driver of MCAS symptoms.
✨ Want to explore your triggers?
MCAS and other triggers
While mould illness is a common factor, it isn’t the only one. Other triggers can include:
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infections (viral, bacterial, tick-borne)
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high toxic load from chemicals or pollutants
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certain foods or medications
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chronic physical or emotional stress
Identifying which triggers are most relevant is an important step in managing MCAS effectively.
How is MCAS diagnosed?
There is no single test for MCAS. Diagnosis is usually based on:
- a careful clinical history and symptom pattern
- exclusion of other conditions
- sometimes laboratory markers (such as tryptase, histamine, or prostaglandin levels
Because symptoms overlap with many other illnesses, diagnosis requires experience and a whole-person view.
Treatment approach for MCAS
My approach to MCAS is two-fold:
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Calm the mast cells
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Support with treatments that reduce mast cell overactivation and ease symptoms.
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Identify and address root causes
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For many patients, this means uncovering hidden triggers such as mould and other biotoxins, toxins, infections or sensitivities.
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Over time, this helps reduce the need for mast cells to stay on “high alert,” breaking the cycle of inflammation, and restoring a more balanced immune response.
