Skip to main content
OpenTrials
Completed

NCT Number: NCT07006558

Kinetic Study Of Supplementation With The Enzyme Diamine Oxidase In Patients With Histamine Intolerance

The present study was conducted to assess the safety and tolerability of five ascending doses of plant-based DAO enzyme supplement in subjects with symptoms of histamine intolerance.

Completed

Looking for future studies?

Notify Me

Key information

Conditions

Histamine Intolerance

Age range

18 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Hospital Clinic de Barcelona

Barcelona, 08036, Spain

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Recent history of 2 or more symptoms associated to histamine intolerance.
  • Altered activity of plasmatic DAO enzyme and/or at least one genetic variants linked to DAO deficiency (rs10156191, rs1049742, rs1049793, rs2052129).
  • Not having started a dietary intervention (low histamine diet or DAO supplementation) before the start of this study.

Exclusion criteria

  • Treatment with low-histamine diet and/or dietary DAO enzyme supplementation prior to the study.
  • Pharmacological treatment with antibiotics or probiotic supplements within the last month prior to enrollment.
  • Breast-feeding or pregnant women.
  • Inability to provide informed consent.

Treatment and study plan

Diamino Oxidase

Dietary Supplement

The investigational product is a dehydrated power of DAO enzyme from green pea (Pisum sativum L.) sprouts (adiDAO®Veg, DR Healthcare, S.L.U., Barcelona, Spain), with an enzymatic activity > 298 mU/g (> 14,500 kHDU/g).

Primary outcomes

  1. Number of participants with treatment-related adverse events (AEs)

    Time frame: At "day 14", "day 28", "day 42", "day 56" and "day 70".

    Number of participants with treatment-related adverse events (AEs) experienced during the supplementation, assessed through a questionnaire.

  2. Type of adverse effects (AEs)

    Time frame: At "day 14", "day 28", "day 42", "day 56" and "day 70".

    Symptoms of adverse effects (AEs) experienced during the supplementation, assessed through a questionnaire including the different body systems: gastrointestinal, CNS, respiratory, dermatological).

  3. DAO enzymatic activity in serum using a radioextraction immunoassay

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    DAO enzymatic activity in serum (mU/mL) using a radioextraction immunoassay (REA-3H, Laboratorio Echevarne, Barcelona, Spain).

Secondary outcomes

  1. Dietary habits

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Dietary habits assessed through a dietary weekly record

  2. Histamine in 24h urine

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Histamine in 24h urine

  3. Hemogram

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Hemogram

  4. Glycemia

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Glycemia for safety assessment

  5. HbA1c

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    HbA1c for safety assessment

  6. Ionogram

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Ionogram for safety assessment

  7. Lipid profile

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Lipid profile

  8. C-reactive protein

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    C-reactive protein for safety assessment

  9. Interleukin-6

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Interleukin-6 for safety assessment

  10. Proteinuria

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Proteinuria from urine sample

  11. Urine sediment

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Urine sediment from urine sample for safety assessment

  12. Gastrointestinal symptoms through Rome IV criteria

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported Gastrointestinal symptoms: Rome IV criteria

  13. Gastrointestinal symptoms through Bristol Stool Scale

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported Gastrointestinal symptoms: Bristol Stool Scale. Score goes from Type 1 to Type 7. Higher and lower scores mean worse outcome. Middle scores (Type 3-4) are considered normal/healthy stool consistency.

  14. Gastrointestinal symptoms through Gastrointestinal Quality of Life Index (GIQLI)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported Gastrointestinal symptoms: Gastrointestinal Quality of Life Index (GIQLI). Score goes from 0 to 144. Higher scores indicate a better outcome.

  15. Headaches symptoms through MIDAS questionnaire

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported Headaches symptoms through Migraine Disability Assessment Questionnaire (MIDAS) questionnaire. Score goes from 0 to >21 points. Higher scores indicate a worse outcome.

  16. Headaches symptoms through HIT-6 questionnaire

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported Headaches symptoms through Headache Impact Test-6 (HIT-6) questionnaire. Score goes from 36 to 78. Higher scores indicate a worse outcome.

  17. Respiratory symptoms through SNOT-22 questionnaire

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported respiratory symptoms through Sino-Nasal Outcome Test-22 (SNOT-22) questionnaire. Score goes from 0 to 110. Higher scores indicate a worse outcome.

  18. Respiratory symptoms through Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ). Score goes from 0 to 6. Higher scores indicate a worse outcome.

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported respiratory symptoms through Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ)

  19. Dermatological symptoms through SCORAD index

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported dermatological symptoms through SCORing Atopic Dermatitis (SCORAD) index. Score goes from 0 to 103. Higher scores indicate a worse outcome.

  20. Dermatological symptoms through Itch Severity Scale (ISS)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported dermatological symptoms through Itch Severity Scale. Score goes from 0 to 21. Higher scores indicate a worse outcome

  21. Dermatological symptoms through Dermatology Life Quality Index (DLQI)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported dermatological symptoms through Dermatology Life Quality Index (DLQI). Score goes from 0 to 20. Higher scores indicate worse outcomes.

  22. Short-Form Health Survey (SF-36)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Self-reported Short-Form Health Survey (SF-36) Quality of Life. Score goes from 0 to 100. Higher scores indicate a better outcome.

  23. Creatinine (mg/dL)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Creatinine (mg/dL) to assess renal function

  24. Glomerular filtration rate (mL/min/1.73m2)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Glomerular filtration rate (mL/min/1.73m2) to assess renal function

  25. Uric acid (mg/dL)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Uric acid (mg/dL) to assess renal function

  26. Albuminuria (mg/L)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Albuminuria (mg/L) to assess renal function

  27. Albumin/creatinine ratio

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Albumin (mg/L)/creatinine (mg/dL) ratio; to assess renal function

  28. Urine (mg/g)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Urine (mg/g) ratio; to assess renal function

  29. Urinary pH

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Urinary pH to assess renal function

  30. Urine specific gravity (g/mL)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Urine specific gravity (g/mL) to assess renal function

  31. Aspartate Aminotransferase, ASAT (U/L)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Aspartate Aminotransferase, ASAT (U/L) to assess hepatic function

  32. Alanine Aminotransferase, ALAT (U/L)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Alanine Aminotransferase, ALAT (U/L) to assess hepatic function

  33. Gamma-Glutamyl Transferase, GGT (U/L)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Gamma-Glutamyl Transferase, GGT (U/L) to assess hepatic function

  34. Total Bilirubin (mg/dL)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Total Bilirubin (mg/dL) to assess hepatic function

  35. Alkaline Phosphatase (U/L)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Alkaline Phosphatase (U/L) to assess hepatic function

  36. Lactate Dehydrogenase (U/L)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Lactate Dehydrogenase (U/L) to assess hepatic function

  37. Total Proteins (g/L)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Total Proteins (g/L) to assess hepatic function

  38. Albumin (g/L)

    Time frame: At "baseline or day 1", "day 14", "day 28", "day 42", "day 56" and "day 70".

    Albumin (g/L) to assess hepatic function

Sponsors and collaborators

Lead sponsor

AB Biotek

Industry

Collaborators

  • Hospital Clinic of Barcelona

Registry information

Acronym: HCB/2023/0345

Important dates

Study start
2023
Primary completion
2024
Study completion
2024
First posted
Jun 5, 2025
Registry last updated
Jun 18, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Related clinical trials

Published trials that share one or more normalized conditions with this study.