Why your body is reactive to everything — food, supplements, chemicals & stress (histamines & mast cells)
There's a point some people reach where the question stops being "what am I reacting to" and becomes "what am I not reacting to."
Food. Supplements that should help. Fragrances. Cleaning products. Other people's perfume. Medications. Stress. Exercise. Temperature changes. The list of triggers expands until it feels like the body has declared war on the world around it.
This is one of the most distressing and least understood patterns in complex chronic illness. And it’s almost never explained adequately.
This is not imaginary. This is your body overwhelmed. The reactivity is its attempt to protect itself from a threat load that has exceeded its capacity to manage.
what's happening biologically
The core mechanism in this pattern is mast cell activation.
Mast cells are immune cells found throughout the body — in the gut, skin, lungs, brain, and connective tissue. Their job is to detect threats and mount an immune response — releasing histamine and other inflammatory mediators to signal danger and drive the defensive response.
In a healthy, well-regulated immune system, mast cells activate in response to genuine threats — pathogens, toxins, injury — and then return to baseline when the threat has passed.
In the pattern of expanding reactivity, mast cells have become chronically primed. They are activating in response to stimuli that should be innocuous — foods, supplements, environmental chemicals, stress hormones, temperature fluctuations — because the threshold for activation has been dramatically lowered.
This threshold lowering happens because of the total burden the system is carrying. Not any single trigger — the accumulated load.
what lowers the mast cell activation threshold
Several drivers consistently appear in this picture:
Mould and mycotoxin exposure — mycotoxins are among the most potent known triggers of mast cell activation. They prime mast cells directly, increase their reactivity, and impair the regulatory mechanisms that normally keep activation in check. Women with unrecognised or inadequately addressed mould exposure almost universally develop significant mast cell reactivity over time.
Gut dysfunction — the gut contains the highest concentration of mast cells in the body. Intestinal permeability allows compounds into the bloodstream that activate mast cells systemically. Dysbiosis disrupts the immune regulatory environment that normally keeps mast cell activity calibrated.
Chronic nervous system activation — the autonomic nervous system directly regulates mast cell behaviour. A nervous system chronically running in threat response maintains mast cells in a primed state — because physiologically, threat response and immune activation are coordinated. The body cannot fully downregulate immune reactivity while the nervous system is maintaining a threat signal.
Histamine accumulation — mast cells release histamine, and histamine itself primes mast cells further. This creates a self-reinforcing loop where each activation event lowers the threshold for the next one.
Nutritional depletion & genetics— specific nutrients regulate mast cell function and histamine metabolism. Vitamin C, B6, copper, magnesium and quercetin all support DAO enzyme activity and histamine clearance. When these are depleted, or we are genetically not pre-dispositioned to break down histamines — the capacity to clear histamine after each mast cell activation event is reduced.
why supplements stop being tolerated
This is one of the most confusing aspects of this pattern — and one that causes significant distress.
Supplements that should help — probiotics, fish oil, vitamin C, magnesium — begin causing reactions. The person trying to address their health finds that the tools available to them have become part of the problem.
Several mechanisms explain this lack of tolerance
Many supplements contain histamine or trigger histamine release. Fermented probiotics, certain fish oils, vitamin C in high doses, and a range of herbal supplements all have histamine-relevant properties that can worsen the picture in a highly reactive person. Even quercetin can be intolerable for some people.
A gut that is highly inflamed and reactive cannot process supplemental compounds normally. What would be a therapeutic dose in a less compromised system becomes an inflammatory trigger in one that is already overwhelmed.
So the sequence matters enormously. Attempting aggressive supplementation before stabilising the mast cell environment and reducing the overall inflammatory burden is one of the most common reasons supplementation fails or worsens the picture in this population.
the chemical sensitivity dimension
As mast cell reactivity increases and the gut-brain-immune system becomes increasingly sensitised, chemical sensitivity frequently develops or worsens.
Fragrances, cleaning products, vehicle exhaust, pesticides, synthetic materials — compounds that others tolerate without awareness begin causing neurological symptoms, fatigue, pain, or cognitive dysfunction in people with this pattern.
This is not psychological. It is the result of a sensitised immune and nervous system responding to chemical compounds that, at the exposure levels being encountered, are being interpreted as threats. The limbic system — the brain's threat-detection centre — becomes increasingly sensitised alongside the immune system, lowering the threshold for neurological reactivity in parallel with immunological reactivity.
the path through
The approach that works in this picture is almost the opposite of what instinct suggests.
Instinct suggests — identify all the triggers and eliminate them. Add supplements to address the deficiencies. Push through the reactivity.
What actually works — reduce the total burden. Address the underlying drivers rather than chasing individual triggers. Create the conditions for the mast cell activation threshold to rise again, so that stimuli that are currently triggers return to being tolerable.
This means
Addressing mould burden — if mycotoxin exposure is part of the picture, it must be addressed. It cannot be managed around indefinitely.
Stabilising the gut — not aggressively, but systematically. Starting with what the body can tolerate and building very gradually. The gut environment is the immune environment.
Supporting the nervous system — because mast cell reactivity cannot fully resolve while the autonomic nervous system is maintaining a chronic threat signal. Approaches that support parasympathetic activation — that give the body physiological signals of safety — are part of the biology here, not an optional adjunct.
Strategic nutritional support — low-histamine, low-reactive, targeted. Not everything at once. Understanding which nutrients support mast cell regulation without triggering further reactivity.
Patience with the process — because the sensitisation that has developed over months or years does not resolve in weeks. The threshold rises gradually, as the total burden decreases and the regulatory systems recover.
what this is not
This is not a psychological condition. It is not hypochondria. It is not an anxiety disorder that has been medicalised. It is a real, biological state with documented mechanisms — and it resolves when those mechanisms are addressed.
The body that has become reactive to everything has not given up. It is fighting, with everything it has, against a burden it was not designed to carry indefinitely. Understanding that — and working with it rather than against it — is where things begin to change.
Nore Hoogstad is a Functional Nutritionist & Psych-K Practitioner specialising in complex, unresolved health cases in women. A free 20-minute call is available — come and tell the story. Book here.