Private GP | Thyroid Health and Functional Medicine

Opening Hours : Monday to Thursday: 9:00-12:00 & 13:00-16:00 Friday: 9:00-12:00
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Advanced Intestinal Barrier Assessment




Zonulin is a non-invasive marker of gut wall integrity. It plays an important role in the opening of small intestine tight junctions. Increased levels of zonulin are linked with:

  • Autoimmune diseases
  • Cancers
  • Diseases of the nervous system

Diamine oxidase

DAO is the body’s primary enzyme for breaking down ingested histamine and a natural defence against histamine excess. If you ingest too much dietary histamine or produce more than your DAO level can handle, reactions can occur. DAO is produced in the small intestine but certain drugs, foods and bacteria may suppress its production.



Histamine is involved in many types of allergic and inflammatory processes. It also acts as a neurotransmitter and regulates physiological function in the gastrointestinal tract.

Histamine imbalances in the body may cause a variety of adverse effects ranging from life-threatening allergic reactions to localised itching, runny nose or hives.

An excess of histamine may be a result of ingested histamine (certain foods), released histamine from storage sites in the body (from food or environmental triggers), or a diamine oxidase deficiency (needed for the breakdown of histamine).

How to order the test

To order the test, please click on the button below and use the Patient Login with these details:

  • User: oliverfrey
  • Password: client


SKU: Invivo: DUN5150 Categories: , ,


Sample type:  Blood, Plasma – an additional phlebotomy charge will apply!

Turnaround time: 15 days

Sample report: Click HERE

High histamine levels are associated with the following symptoms and conditions:

•Severe allergic reactions (anaphylaxis)
•Low muscle tone
•High blood pressure
•Nausea, vomiting
•Diarrhoea, gas
•Intestinal cramps
•Painful menstruation
•Shortness of breath
•Congestion, runny nose, sneezing
•Hives, itching, flushing
•Abnormal heart rate
•Changes in Circadian rhythm, Body temperature, Food intake, Learning.

Low DAO levels are associated with the following symptoms and conditions:

•Migraine, headache
•Chronic fatigue
•Hives, skin rash, eczema, psoriasis
•Nasal congestion, asthma
•Gastrointestinal disorders, inflammation, irritable bowel syndrome
•Dysmenorrhea, PMS, oestrogen dominance
•Arrhythmia, hypertension, hypotension
•Fibromyalgia, muscular pain
•Rheumatoid arthritis
•Neurological conditions such as multiple sclerosis and ADHD
•Depression and anxiety

Testing histamine along with diamine oxidase (DAO) levels provides important information that standard food sensitivity tests may not reveal. In fact, many clinicians often suspect food sensitivities when the culprit may actually be histamine intolerance.