Effect of Oral Diamine Oxidase on Symptoms Induced by Histamine Oral Challenge

November 9, 2026 updated by: DR Healthcare - biotexia

Double-Blind, Placebo-Controlled, Crossover Trial to Evaluate the Effect of Diamine Oxidase (DAO) on the Response to Oral Histamine Challenge

The goal of this clinical trial is to learn whether oral diamine oxidase (DAO) can lower symptoms caused by an oral histamine challenge in adults with self-reported food-related histamine symptoms who demonstrate responsiveness to histamine challenge during screening.

Study Overview

Detailed Description

Histamine intolerance is characterized by the occurrence of symptoms after ingestion of histamine-containing foods and may be associated with reduced degradation of dietary histamine by the enzyme diamine oxidase (DAO). Previous studies have suggested potential benefits of oral DAO supplementation; however, additional controlled clinical studies are needed using standardized histamine challenge procedures and predefined symptom assessments.

This study is a randomized, double-blind, placebo-controlled, crossover trial conducted in healthy adult volunteers who demonstrate a predefined response to histamine provocation are randomized into the treatment phase.

Study Type

Interventional

Enrollment (Estimated)

60

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact Backup

Study Locations

    • Barcelona
      • Barcelona, Barcelona, Spain, 08041
        • Recruiting
        • Centre d'Investigació del Medicament (CIM-IR Sant Pau)
        • Contact:
    • Spain
      • Barcelona, Spain, Spain, 08041
        • Recruiting
        • Hospital de la Santa Creu i Sant Pau

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

18 years to 65 years (Adult, Older Adult)

Accepts Healthy Volunteers

Yes

Genders Eligible for Study

All

Description

Inclusion Criteria:

  • Adults aged 18 to 65 years.
  • History of symptoms after consumption of foods potentially rich in histamine.
  • Clinically stable and suitable for oral histamine challenge testing.
  • Ability and willingness to provide informed consent.
  • Willingness to comply with study procedures and restrictions.
  • No clinically relevant medical history.
  • No clinically significant findings during screening assessments.
  • Positive response to histamine challenge during screening, according to predefined protocol criteria.

Exclusion Criteria:

  • Food allergy, celiac disease, peptic ulcer disease, or esophagitis.
  • Acute infection.
  • Pregnancy or breastfeeding.
  • History of anaphylaxis or severe reactions to histamine.
  • Known intolerance to diamine oxidase.
  • Severe chronic diseases or medical conditions that may increase risk.
  • Excessive alcohol consumption.
  • Positive drug or alcohol screening.
  • Use of medications that may interfere with histamine or DAO activity.
  • Severe reaction during screening histamine challenge.
  • Any condition that, in the investigator's opinion, may compromise participant safety or study conduct.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Other
  • Allocation: Randomized
  • Interventional Model: Crossover Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Placebo Comparator: Placebo

Placebo

Matching placebo capsule administered before a standardized oral histamine challenge in a randomized, double-blind, crossover study.

Experimental: DAO

Oral diamine oxidase (DAO) dietary supplement administered before a standardized oral histamine challenge in a randomized, double-blind, crossover study.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Overall symptom burden following oral histamine challenge
Time Frame: 0 to 4 hours after histamine challenge

Overall symptom burden is assessed using a study-specific symptom rating scale covering three domains: gastrointestinal, cutaneous/mucosal, and headache/neurovegetative symptoms. Each domain is rated from 0 (no symptoms) to 10 (maximum imaginable symptom intensity), resulting in a total score ranging from 0 to 30, with higher scores indicating greater symptom burden. The primary outcome is the area under the curve (AUC) of the total symptom score over the first 4 hours following the histamine challenge.

0 to 4 hours after histamine challenge

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

September 1, 2026

Primary Completion (Estimated)

February 1, 2027

Study Completion (Estimated)

June 1, 2027

Study Registration Dates

First Submitted

August 31, 2026

First Submitted That Met QC Criteria

November 9, 2026

First Posted (Actual)

November 13, 2026

Study Record Updates

Last Update Posted (Actual)

November 13, 2026

Last Update Submitted That Met QC Criteria

November 9, 2026

Last Verified

November 1, 2026

More Information

Terms related to this study

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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