Histamine is often misunderstood.
While many people associate it only with allergies, histamine is a naturally occurring compound that plays essential roles throughout the body.
However, in some individuals, histamine levels may accumulate beyond what the body can effectively break down — leading to a pattern of symptoms sometimes referred to as histamine intolerance.
What Is Histamine?
Histamine is a biogenic amine produced by:
• Immune cells (especially mast cells and basophils)
• The gastrointestinal tract
• Certain gut bacteria
It plays important roles in:
• Immune defence
• Gastric acid secretion
• Neurotransmitter regulation
• Sleep–wake cycle
• Body temperature
• Appetite regulation
Histamine in the Immune System
When exposed to allergens or pathogens, histamine is released to:
• Dilate blood vessels
• Increase immune cell access
• Promote inflammation as part of a protective response
For example, redness and swelling after a mosquito bite is partly due to histamine activity.
Histamine in Digestion
Histamine stimulates stomach acid production, which is necessary for:
• Protein digestion
• Mineral absorption
• Protection against pathogens
Histamine in the Nervous System
Histamine acts as a neurotransmitter involved in:
• Wakefulness
• Mood regulation
• Cognitive function
What Is Histamine Intolerance?
Histamine intolerance is not an allergy.
It is thought to occur when the accumulation of histamine exceeds the body’s ability to break it down effectively.
This may happen due to:
• Reduced enzyme activity
• Excess histamine intake
• Increased endogenous release
• Impaired gut integrity
• Chronic inflammation
The result can be a wide range of symptoms affecting multiple systems.
Signs & Symptoms of Histamine Excess
Gastrointestinal
• Bloating
• Nausea
• Diarrhoea
• Reflux / heartburn
• Abdominal pain
Respiratory
• Runny or itchy nose
• Sneezing
• Nasal congestion
• Shortness of breath
Skin
• Flushing
• Hives
• Eczema
• Rosacea
• Acne
Cardiovascular
• Palpitations
• Blood pressure changes
• Dizziness
Neurological
• Brain fog
• Headaches or migraines
• Anxiety
• Irritability
• Insomnia
Other
• Fatigue
• Menstrual irregularities
• Joint discomfort
Symptoms can fluctuate and may worsen after:
• High-histamine foods
• Alcohol
• Stress
• Infection
• Hormonal shifts
Possible Contributors to Elevated Histamine
Histamine accumulation is often multifactorial.
Potential contributors may include:
• Gut dysbiosis
• Small intestinal bacterial overgrowth (SIBO)
• H. pylori infection
• Intestinal permeability
• Chronic inflammation
• Mast cell activation patterns
• Certain medications
• Alcohol intake
• High-oestrogen states
• Nutrient deficiencies
• Genetic polymorphisms affecting DAO or HNMT
How Does the Body Break Down Histamine?
Histamine is metabolised primarily by two key enzymes:
1. DAO (Diamine Oxidase)
Breaks down ingested histamine in the digestive tract.
DAO is produced in the intestinal lining. If gut integrity is compromised, DAO production may decline.
2. HNMT (Histamine-N-Methyltransferase)
Breaks down histamine within tissues, particularly in the central nervous system.
Further metabolism involves monoamine oxidase pathways.
These enzymes require adequate cofactors, including certain B vitamins and minerals, for optimal activity.
The DAO Enzyme
DAO plays a central role in clearing dietary histamine.
Reduced DAO activity may be influenced by:
• Gut inflammation
• Intestinal damage
• Alcohol consumption
• Certain medications (e.g., NSAIDs, some antidepressants)
Some individuals may have genetic variations affecting DAO production.
What About Mast Cell Activation?
Mast cells store and release histamine as part of immune defence.
In some individuals, mast cell activation may be exaggerated or inappropriate, contributing to symptoms.
Triggers may include:
• Infection
• Environmental toxins
• Mould exposure
• Stress
• Hormonal changes
Mast cell activation syndrome (MCAS) is a complex condition requiring specialist assessment and should not be self-diagnosed.
Testing Considerations
Assessment may include:
• DAO activity testing
• Whole blood histamine
• Comprehensive stool microbiome testing
• Organic acids testing
• Genetic polymorphism analysis
• Inflammatory markers
Results must always be interpreted within the broader clinical context.
There is currently no universally accepted diagnostic criteria for histamine intolerance, and assessment is typically based on symptom pattern and response to dietary modification.
Simple Steps to Reduce Histamine Load
If histamine intolerance is suspected, short-term strategies may include:
• Following a low-histamine diet
• Avoiding aged and fermented foods
• Minimising alcohol
• Avoiding foods that may inhibit DAO
• Prioritising fresh, minimally processed foods
A trial period of 1–2 weeks may help determine whether symptoms are histamine-related.
However, long-term restrictive diets are not recommended without professional guidance.
A Balanced Perspective
Histamine intolerance remains an evolving area of research.
While some individuals clearly benefit from histamine-focused interventions, symptoms are often multifactorial and may overlap with:
• Gut dysbiosis
• IBS
• Reflux
• Anxiety disorders
• Hormonal imbalances
A structured, individualised assessment is essential.
When to Seek Professional Support
Seek medical assessment if symptoms are:
• Severe
• Progressive
• Associated with anaphylaxis
• Involving breathing difficulties
• Causing significant quality-of-life impairment
How We Can Help
Gut Health Clinic Australia provides:
• Australia-wide consultations
• Comprehensive microbiome testing
• DAO assessment
• Functional testing for inflammatory and digestive drivers
• Structured personalised protocols
If you suspect histamine intolerance may be contributing to your symptoms, a comprehensive assessment can help clarify next steps.
Sources
Maintz, L., & Novak, N. Histamine and histamine intolerance. American Journal of Clinical
Nutrition.
https://pubmed.ncbi.nlm.nih.gov/19321522/
Schwelberger, H. G. Histamine intolerance: a metabolic disease? Inflammation Research.
https://pubmed.ncbi.nlm.nih.gov/21063724/
Comas-Basté, O., et al. New approach for the diagnosis of histamine intolerance based on
determination of histamine and diamine oxidase. Nutrients.
https://pubmed.ncbi.nlm.nih.gov/29518900/
Afrin, L. B., et al. Diagnosis of mast cell activation syndrome: a global “consensus-2”. Diagnosis.
https://pubmed.ncbi.nlm.nih.gov/32324159/
