Clinical trial NCT05810233: Effect of Vitamin C on Allergy Skin Test
Official title: The Effect of Vitamin C on the Skin Prick Test Wheal Reaction
Study type: INTERVENTIONAL
Overall status: RECRUITING
Phase: NA
Conditions: Rhinitis, Allergic
Allergy
Keywords: ascorbic acid
skin prick test
vitamin C
antihistamine
Lead sponsor: National University of Malaysia
Sponsor class: OTHER
First posted: 2023-04-12
Enrollment: 90
Sex: ALL
Minimum age (years): 18
Maximum age (years): 40
Standard ages: ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: PARALLEL
Intervention model description: Participant assigned to only one intervention per arm either vitamin C or placebo tablets
Primary purpose: DIAGNOSTIC

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

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.

Eligibility criteria: Inclusion Criteria:

* Participants above 18-years old
* Participants with history at least 2 symptoms of rhinitis triggered by dust
* Positive SPT to Dermatophagoides pteronyssinus with wheal reaction of at least 5 mm done within the past 1 year.

Exclusion Criteria:

* Prior skin prick test result form do not include a tracing of the wheal reaction.
* Prior skin prick test was not performed in HCTM.
* Participants who are actively smoking or who have smoked cigarette or vaped in the past 6 months
* Participants with skin conditions affecting the volar aspects of the arm.
* Participants on beta-blockers
* Participants contraindicated for skin prick test (pregnancy, history of anaphylaxis, poorly controlled asthma)
* Participants on long term supplements (multivitamin, traditional supplement)
* Participants contraindicated for vitamin c (vitamin c allergy, kidney dysfunction, history of kidney or bladder stones, hyperuricemia, thalassemia, G6PD deficiency, sickle cell disease, hamatochromatosis)
* Participants at risk of vitamin C deficiency (hyperthyroidism, elderly, beastfeeding, diarrhoea, restricted diet secondary to inflammatory bowel disease, anorexia or cancer)

Primary outcomes:
measure: Skin prick test wheal area of vitamin C group compared to placebo
timeFrame: Day 8
Secondary outcomes:
measure: Skin prick test wheal reaction at day 8 of intevention compraed to prior skin prick test done as standard of care
timeFrame: Day 8
Other outcomes:
Locations:
city: Cheras
country: Malaysia
facility: Hospital Canselor Tuanku Mukhriz
state: WP Kuala Lumpur
Study officials:
affiliation: National University of Malaysia
name: Aneeza K W Hamizan
role: PRINCIPAL_INVESTIGATOR
References:
citation: Skoner DP. Allergic rhinitis: definition, epidemiology, pathophysiology, detection, and diagnosis. J Allergy Clin Immunol. 2001 Jul;108(1 Suppl):S2-8. doi: 10.1067/mai.2001.115569.
citation: Fortner BR Jr, Danziger RE, Rabinowitz PS, Nelson HS. The effect of ascorbic acid on cutaneous and nasal response to histamine and allergen. J Allergy Clin Immunol. 1982 Jun;69(6):484-8. doi: 10.1016/0091-6749(82)90171-3.