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Advanced Intestinal Barrier Assessment 5150*

Includes Diamine Oxidase (DAO), Histamine, and Zonulin.

Advanced IBA 5150

Summary of the Profiles

  • The Advanced Intestinal Barrier Assessment 5150 measures DAO, histamine, and DAO: Histamine ratio, and Zonulin.

Summary of the Biomarkers

  • Diamine oxidase is an enzyme that breaks down histamine.
  • Histamine is a compound that affects immune response, physiological function of the digestive tract, and acts as a neurotransmitter.
  • Zonulin is a eukaryotic protein structurally similar to Vibrio cholerae's zonula occludens toxin. It plays an important role in the opening of small intestine tight junctions.

Advanced Intestinal Barrier Assessment 5150:

  • DAO
  • Histamine
  • Zonulin

Why Test Diamine Oxidase (DAO)?

Diamine oxidase is the body’s primary enzyme for breaking down ingested histamine and a natural defense 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.

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, estrogen dominance
  • Arrhythmia, hypertension, hypotension
  • Fibromyalgia, muscular pain
  • Rheumatoid arthritis
  • Neurological conditions such as multiple sclerosis and attention deficit and hyperactivity disorder (in childhood and adolescence)
  • Depression and anxiety

Symptoms of low DAO are similar to those of histamine excess since it is the DAO that breaks down and metabolizes the histamine. Patients suffering from urticaria (hives), Crohn’s or celiac disease show low DAO activity in serum or plasma.1,2 People with the inability to break down histamine react to many substances and will often improve on antihistamines. Since DAO is made in the gastrointestinal tract, low levels are also indicative of poor digestive function and a compromised intestinal barrier.

Why Test Histamine?

Histamine is involved in many types of allergic and inflammatory processes, including immediate and delayed hypersensitivity reactions. 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 localized 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). 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. An excellent full text review of histamine intolerance is available. 3

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

  • Severe allergic reactions (anaphylaxis)
  • Low muscle tone
  • High blood pressure
  • Dizziness
  • Headache
  • Nausea, vomiting
  • Diarrhea, 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
    • Memory
    • Locomotion


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

  • Fatigue
  • Depression
  • Sleep-wake disorders such as narcolepsy
  • Convulsions
  • Seizures

What is The DAO: Histamine Ratio?

The DAO: Histamine Ratio helps detect subtle imbalances between histamine and DAO levels. Even if the DAO enzyme level is normal when histamine is high, symptoms can occur. A low ratio indicates that there may not be enough of the DAO enzyme relative to the amount of histamine in your body.

Why Test Zonulin? (5150)

Zonulin plays an important role in the opening of small intestine tight junctions. The loss of gut wall integrity during conditions such sepsis might be pivotal and has been described in various experimental involving human studies. As mentioned previously, increased levels of zonulin could also be demonstrated in diseases associated with increased intestinal inflammation, such as celiac disease and type 1 diabetes. Therefore we measure this molecule as a non-invasive marker of gut wall integrity.5

What Should I Do Before I Take This Test?

  • Inform your practitioner of all medications and supplements you are currently taking.
  • Arrange plasma collection for Monday-Thursday.
  • See blood draw collection instructions inside test kit.

How Are Imbalances in DAO, Histamine and Zonulin Treated?

When DAO or histamine is imbalanced, the main focus of treatment is to increase DAO, reduce histamine, and heal the gut. The primary focus of treatment for elevated zonulin levels is to correct intestinal permeability and restore a healthy balance of gut flora. Treatments might include dietary changes, enzymes, probiotics, antimicrobial herbal formulas, and supplements designed to improve the integrity of the gastrointestinal lining.

Further Testing

Consider Comprehensive Stool Analysis and C3d/IgG Food Sensitivity testing to reveal additional underlying causes of intestinal permeability.


  1. Schmidt WU, Sattler J, Hesterberg R, et al. Human intestinal diamine oxidase (DAO) activity in Crohn's disease: a new marker for disease assessment? Agents and actions. Apr 1990;30(1-2):267-270.
  2. Corazza GR, Falasca A, Strocchi A, Rossi CA, Gasbarrini G. Decreased plasma postheparin diamine oxidase levels in celiac disease. Digestive diseases and sciences. Aug 1988;33(8):956-961.
  3. Maintz L, Novak N. Histamine and histamine intolerance. Am J Clin Nutr. May 2007;85(5):1185-1196.
  4. Banks WA, Robinson SM. Minimal penetration of lipopolysaccharide across the murine blood-brain barrier. Brain, behavior, and immunity. Jan 2010;24(1):102-109.
  5. Yue G, Shi G, Azaro MA, et al. Lipopolysaccharide (LPS) potentiates hydrogen peroxide toxicity in T98G astrocytoma cells by suppression of anti-oxidative and growth factor gene expression. BMC genomics. 2008;9:608.