Understanding What Drives Histamine Intolerance &
Why the Nervous System Matters

Histamine intolerance is often described as a food problem, but for most people it is far more complex than reacting to a few “high-histamine foods.”

Histamine is a natural chemical involved in digestion, immune defence and nervous system signalling. Symptoms arise when histamine builds up faster than the body can break it down.

Histamine intolerance is not a diagnosis on its own. It is a functional pattern that reflects how digestion, the microbiome, the immune system and the nervous system are working together.

What Histamine Intolerance Really Is

In a healthy system, histamine is broken down by enzymes in the gut and liver, particularly DAO (diamine oxidase).

Problems develop when histamine production increases, breakdown is reduced, or both.

Common contributors include:

  • dysbiosis or bacterial overgrowth that produces histamine

  • SIBO, especially certain bacterial strains

  • low stomach acid or weak digestive enzymes

  • impaired DAO enzyme activity

  • nutrient deficiencies, particularly B6, copper and vitamin C

  • intestinal inflammation or increased permeability

  • hormonal fluctuations, especially around the menstrual cycle

  • chronic stress

  • long-term use of certain medications, including painkillers and antidepressants

This is why histamine symptoms often overlap with IBS, bloating, reflux, food sensitivities, migraines and skin reactions.

The Gut–Brain Axis

Histamine is closely linked to the nervous system and stress response.

When the body enters fight, flight, freeze or shutdown, histamine release increases as part of the immune and alertness response. At the same time, digestion and enzyme production often decrease, making histamine harder to break down.

Many people notice symptoms worsen during:

  • stressful periods

  • poor sleep

  • emotional strain

  • overtraining or physical exhaustion

  • hormonal shifts

For some, histamine reactions become another way the body expresses being stuck in a state of threat.

Why Common Histamine Intolerance Advice Falls Short

Low-histamine diets can reduce symptoms, but they often do not address:

  • why histamine production is high

  • why breakdown enzymes are impaired

  • why the gut lining is inflamed or permeable

  • or why the nervous system remains overactivated

This can lead to increasingly restrictive eating without true resolution.

What Actually Helps Long Term

Lasting improvement comes from reducing the overall histamine load and restoring the body’s ability to regulate it.

This often involves:

Supporting digestion
Improving stomach acid and enzyme output.

Balancing the microbiome
Reducing histamine-producing bacteria and supporting beneficial species.

Healing the gut lining
Lowering inflammation and permeability.

Rebuilding key nutrients
That support DAO and histamine breakdown.

Supporting hormonal balance
When symptoms fluctuate with the cycle.

Regulating the nervous system
Reducing chronic stress signalling that increases histamine release.

Gradually expanding the diet
As tolerance improves.

When these layers are addressed together, histamine reactions often become less frequent, less intense and far more predictable.

TLDR

What drives histamine intolerance
Histamine intolerance develops when production outweighs breakdown due to digestive impairment, microbial imbalance, inflammation, nutrient deficiencies and stress physiology.

The role of the nervous system
Stress states increase histamine release and reduce digestive enzyme activity, making symptoms more likely and harder to control.

In short
Histamine intolerance is rarely just about food. It reflects a digestive–immune–microbiome–nervous system pattern. When these systems are supported together, tolerance often improves.

This is the Mind–Body–Biome approach.