Effect of Vitamin C on Allergy Skin Test

National University of Malaysia (Other)
Overall Status
Not yet recruiting
CT.gov ID

Study Details

Study Description

Brief Summary

This study will assess the effect of taking vitamin C on allergy skin test.

Condition or Disease Intervention/Treatment Phase
  • Dietary Supplement: Ascorbic acid 1000mg

Detailed Description

Allergic rhinitis (AR) is an Immunoglobulin E (IgE) mediated inflammation of the nasal cavity. House dust mite is the most common causative allergen. The skin prick test is the preferred method to confirm allergy. This test is interpreted by measuring the skin wheal reaction in response to allergen application and histamine. Prior studies have shown that Vitamin C may have antihistamine effect that may reduce the wheal reaction in skin prick test thus cause difficulties to interpret the results. Current guidelines do not recommend cessation of vitamin C prior to skin prick test. This will require further study in order to further understand the effect of vitamin C in commercially available dose on the skin prick test wheal reaction. In this randomized placebo controlled trial, consecutive participant visiting the ENT clinic with allergic rhinitis and prior positive skin prick test towards dust mite will be screened for inclusion and exclusion criteria. Participants will either receive vitamin C 1000mg daily for 7 days or placebo. The skin prick test will be performed after one week of intervention and the area of the wheal reaction area (mm2) and longest diameter (mm) recorded. This will be compared between the two groups. The expected outcome is that participants with oral supplementation of vitamin C will have reduced SPT wheal reaction compared to placebo group.

Study Design

Study Type:
Anticipated Enrollment :
90 participants
Intervention Model:
Single Group Assignment
Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary Purpose:
Official Title:
The Effect of Vitamin C on the Skin Prick Test Wheal Reaction
Anticipated Study Start Date :
May 1, 2023
Anticipated Primary Completion Date :
Sep 30, 2023
Anticipated Study Completion Date :
Oct 30, 2023

Arms and Interventions

Arm Intervention/Treatment
Experimental: Vitamin C

Commercially available Tablet Vitamin C 1000mg per day for 7 days

Dietary Supplement: Ascorbic acid 1000mg
Health supplement
Other Names:
  • VItamin C
  • Placebo Comparator: Placebo

    Sucrose tablets 1 per day

    Dietary Supplement: Ascorbic acid 1000mg
    Health supplement
    Other Names:
  • VItamin C
  • Outcome Measures

    Primary Outcome Measures

    1. Skin prick test wheal area of vitamin C group compared to placebo [Day 8]

      Skin wheal reaction is measured using computer software. Day 8 wheal area of vitamin C group compared to placebo.

    Secondary Outcome Measures

    1. Skin prick test wheal reaction at day 8 of intevention compraed to prior skin prick test done as standard of care [Day 8]

      Skin wheal reaction are is measured from prior skin test record (baseline) and at day 8 skin test repeated and measured. Area at day 7 - baseline.

    Eligibility Criteria


    Ages Eligible for Study:
    18 Years to 40 Years
    Sexes Eligible for Study:
    Accepts Healthy Volunteers:
    Inclusion Criteria:
    1. Participants above 18-years old 2) Participants with history at least 2 symptoms of rhinitis triggered by dust 3) Positive SPT to Dermatophagoides pteronyssinus with wheal reaction of at least 5 mm done within the past 1 year.
    Exclusion Criteria:
    1. Prior skin prick test result form do not include a tracing of the wheal reaction.

    2. Prior skin prick test was not performed in HCTM.

    3. Participants who are actively smoking or who have smoked cigarette or vape in the past 6 months

    4. Participants with skin conditions affecting the volar aspects of the arm.

    5. Participants on beta-blockers

    6. Participants contraindicated for skin prick test (pregnancy, history of anaphylaxis, poorly controlled asthma)

    7. Participants on long term supplements (multivitamin, traditional supplement)

    8. Participants contraindicated for vitamin c (vitamin c allergy, kidney dysfunction, history of kidney or bladder stones, hyperuricemia, thalassemia, G6PD deficiency, sickle cell disease, hamatochromatosis)

    9. Participants at risk of vitamin C deficiency (hyperthyroidism, elderly, beastfeeding, diarrhoea, restricted diet secondary to inflammatory bowel disease, anorexia or cancer)

    Contacts and Locations


    No locations specified.

    Sponsors and Collaborators

    • National University of Malaysia


    • Principal Investigator: Aneeza K W Hamizan, National University of Malaysia

    Study Documents (Full-Text)

    None provided.

    More Information


    Responsible Party:
    ANEEZA KHAIRIYAH WAN HAMIZAN, Associate Professor, Dr, National University of Malaysia
    ClinicalTrials.gov Identifier:
    Other Study ID Numbers:
    • JEP-2023
    First Posted:
    Apr 12, 2023
    Last Update Posted:
    Apr 12, 2023
    Last Verified:
    Mar 1, 2023
    Individual Participant Data (IPD) Sharing Statement:
    Plan to Share IPD:
    Studies a U.S. FDA-regulated Drug Product:
    Studies a U.S. FDA-regulated Device Product:
    Keywords provided by ANEEZA KHAIRIYAH WAN HAMIZAN, Associate Professor, Dr, National University of Malaysia
    Additional relevant MeSH terms:

    Study Results

    No Results Posted as of Apr 12, 2023