Reliability of Expired Allergens in Patch Testing: A Comparative Study With Non-Expired Series

August 10, 2026 updated by: Laurie Parsons, University of Calgary
Patch testing remains the gold standard in the diagnosis of allergic contact dermatitis. Patches used in testing consist of a wide spectrum of allergens, with variability in the stability of products over time. Due to limited allergen stability, careful storage and preparation is needed to prevent product degradation over time. Expiration dates are provided by manufacturers to ensure stability and reactivity, while minimizing the risk of product degradation contributing to inaccurate testing results. Preparation of patch series can be time intensive and procurement of allergens comes with an associated economic burden. Expired allergens are not routinely used in patch testing, however many clinics have expired allergens accessible. There is paucity of evidence comparing the reactivity of expired vs non-expired patch series. If expired allergens remain effective, this could result in significant cost-savings and accessibility implications for dermatology practice.

Study Overview

Status

Not yet recruiting

Conditions

Intervention / Treatment

Detailed Description

In brief, review of the medical literature showed two comparable studies out of India and Spain suggesting that expired allergen series may be used beyond their labeled expiry dates, with some variability noted amongst duration of expiry, that the investigators will also aim to analyze.

Regarding allergen stability, there were also several studies focused on this domain. The European Society of Contact Dermatitis (ESCD) released guidelines in 2015, outlining optimal methods for allergen storage such as storage at 4 degrees celsius and strict protection from ultraviolet light exposure. While most allergens are dispersed in petrolatum (white soft paraffin), some substances are better tested in solutions such as water (aqueous) or ethanol. Several allergens with high vapour pressure require more frequent renewal and strict storage conditions such as fragrance chemicals, acrylates and isocyanates. Other substances such as glutaraldehyde in petrolatum (pet.) and formaldehyde in aqueous solution (aq.) are susceptible to instability and deterioration. An additional study assessed volatility over time of several select compounds and described high volatility in acrylates, glutaraldehyde, and fragrances, while describing partial volatility of formaldehyde and low volatility of nickel sulfate.

Study participants will include all eligible adults seen in patch testing clinic who maintain an indication for patch testing and consent to participation. The study will be utilizing 10 allergens from the North American Contact Dermatitis Group (NACDG) 80 Series for inclusion in the study.

The allergen selections are primarily based on compounds with a higher likelihood for volatility, in addition to inclusion of two comparator compounds with lower volatility. Expiration intervals include 1 year, 2 years, 3 years, and 4 years. The compounds selected are as follows, including their dispersion compound: nickel sulfate hexahydrate (5% pet.), cobalt (II) chloride hexahydrate (2.5% pet.), hydroperoxides of linalool (1% pet.), hydroperoxides of limonene (0.3% pet.), fragrance mix 1 (8.0% pet.), myroxylon pereirae resin (balsam of Peru) (25.0% pet.), methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) (0.02% aq.), formaldehyde (2.0% aq.), tixocortol-21-pivalate (1.0% pet.), and budesonide (0.1% pet.).

The patch testing results will be compared to corresponding non-expired allergens from the same manufacturer with the same preparation tested simultaneously. Both series will be placed simultaneously in differing locations on the participant's back, ensuring both are placed in sun protected areas with no underlying dermatitis.

Once in clinic, standard patch test series are applied on patch testing day, with the participant instructed not to shower or scratch the area throughout testing. At 48h, the patches are removed and photos are taken of the participant's back which are sent to the Dermatologist for virtual reading. At either 96h or 120h, the participant returns to the clinic for final reading. Both morphology and intensity of positives are graded on a standard patch test scale (irritant reaction), +/- for doubtful, + for erythema and infiltration, ++ for edematous or vesicular and +++ for spreading, bullous or ulcerative. Positive allergens scored + or greater are considered a true allergic contact allergen and assessed for relevance based on clinical context. The Dermatologist provides information sheets on all positive allergens, counsels on the relevance to their clinical history and allergen avoidance going forward, as well as providing the participant with a safe product list via the ACDS Contact Allergen Management Program (CAMP) database.

The investigators are aiming for enrolment of 100 participants which should theoretically provide the study with at least 5-10 participants testing positive to each of the four listed allergens with higher volatility and 20+ participants testing positive to the allergens with lower volatility. The investigators are aiming to assess concordance between expired and non-expired allergen reactions (positive vs negative), in addition to agreement in reaction intensity, differences in morphology, rates of false positives/negatives compared to control and concordance of irritant reaction between interventions.

The study will serve to lend valuable evidence as to whether expired allergens maintain clinical utility and could serve to reduce product waste, lower the economic burden and further improve accessibility of patch testing for use in resource limited settings.

Study Type

Interventional

Enrollment (Estimated)

100

Phase

  • Phase 4

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 Locations

  • Canada
    • Alberta
      • Calgary, Alberta, Canada, T2T 5C7
        • Richmond Road Diagnostic Treatment Centre
        • Contact:
        • Principal Investigator:
          • Laurie Parsons, Medical Doctor

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

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Adults (age 18 years or older) referred for patch testing.

Exclusion Criteria:

  • Relative or absolute contraindication to patch testing
  • Wide spread dermatitis prior to patch placement
  • Inability to return to clinic for reading of results
  • Patient non-consenting

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: Diagnostic
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Other: Enrolled Study Participants
All enrolled participants will be simultaneously patch tested with both expired and non-expired patches. Therefore, there is no difference in intervention amongst study participants.
Biological: Patch 1 (Expired)
All enrolled participants will be simultaneously patch tested with both expired and non-expired patches. Therefore, there is no difference in intervention amongst study participants.
Biological: Patch 2 (non-expired)
All enrolled participants will be simultaneously patch tested with both expired and non-expired patches. Therefore, there is no difference in intervention amongst study participants.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Patch Testing Response (Positive/Negative) Concordance Rate (%) Between Non-Expired and Expired Allergens
Time Frame: Standard patch test series are applied on Day 0. Participant removal of patches on Day 2 and self photos taken and sent to Dermatologist for virtual reading. Final reading completed in clinic by Dermatologist on Day 4 or 5, recording reaction scores.
Each allergen will be graded on response using a standard patch test scale including: irritant reaction ['IR'], '+/-' for doubtful, '+' for erythema and infiltration, '++' for edematous or vesicular and '+++' for spreading, bullous or ulcerative response that will be graded by the participating Dermatologist. Reactions graded '+', "++", or "+++" are consider a positive result. Concordance rate will be expressed as a percentage (%) between tested allergens that were non-expired and that were expired (i.e. Nickel sulfate hexahydrate was found to have a 92% concordance rate, meaning that in 92% of cases, the Nickel allergen in the non-expired and expired patches were both found to both be either positive or negative while in 8% of cases the response differed per the scale listed above.)
Standard patch test series are applied on Day 0. Participant removal of patches on Day 2 and self photos taken and sent to Dermatologist for virtual reading. Final reading completed in clinic by Dermatologist on Day 4 or 5, recording reaction scores.

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Reaction/Morphology Scoring Concordance (%)
Time Frame: Standard patch test series are applied on Day 0. Participant remove patches on Day 2, photos taken and sent to Dermatologist for virtual reading. Final reading completed in clinic by Dermatologist on Day 4 or 5, recording reaction scores, morphology.
For each positive allergen, severity (i.e. '+/-', '+', '++', "+++") and morphology (i.e. erythema, infiltration, edematous, vesicular, bullous, ulcerated) will be recorded. Concordance rate will be expressed as a percentage (%) between tested allergens that were non-expired and that were expired (i.e. Nickel sulfate hexahydrate was found to have a 92% concordance rate, meaning that in 70% of cases, the Nickel allergen in the non-expired and expired patches were both found to have the exact same severity and morphology, while in 30% of cases the severity and/or morphology differed per the scale listed above.)
Standard patch test series are applied on Day 0. Participant remove patches on Day 2, photos taken and sent to Dermatologist for virtual reading. Final reading completed in clinic by Dermatologist on Day 4 or 5, recording reaction scores, morphology.
Stability Concordance (%) Amongst Mediums
Time Frame: Standard patch test series are applied on Day 0. Participant remove patches on Day 2, photos taken and sent to Dermatologist for virtual reading. Final reading completed in clinic by Dermatologist on Day 4 or 5, recording reaction scores, morphology.
Each allergen is suspended within a medium, either petrolatum or aqueous solution. Not only will concordance (%) of positive and negative reactions be assessed amongst allergens and compared between non-expired and expired, but also between mediums to determine if there is a difference in stability over time amongst mediums used to determine if particular mediums result in degradation over time.
Standard patch test series are applied on Day 0. Participant remove patches on Day 2, photos taken and sent to Dermatologist for virtual reading. Final reading completed in clinic by Dermatologist on Day 4 or 5, recording reaction scores, morphology.
Irritant Reaction Rates (%)
Time Frame: Standard patch test series are applied on Day 0. Participant remove patches on Day 2, photos taken and sent to Dermatologist for virtual reading. Final reading completed in clinic by Dermatologist on Day 4 or 5, recording reaction scores, morphology.
Final patch reading will score reactions on a standarized scale, with irritant reaction representing a negative reaction. However, we will compare rates and concordance (%) of irritant reactions between allergens to determine if their is reproducibility, or if expired allergens result in differing rates of irritant reactions. (i.e. Nickel sulfate allergen was shown to have a 50% increased rate of irritant reactions between the expired to non-expired allergens, meaning that Nickel resulted in an irritant reaction in 6 cases of the expired Nickel and 4 cases of the non-expired Nickel, suggesting that expired Nickel allergens may become more irritating over time, resulting in more irritant reactions.
Standard patch test series are applied on Day 0. Participant remove patches on Day 2, photos taken and sent to Dermatologist for virtual reading. Final reading completed in clinic by Dermatologist on Day 4 or 5, recording reaction scores, morphology.

Collaborators and Investigators

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

Sponsor

University of Calgary

Investigators

  • Principal Investigator: Laurie Parsons, Medical Doctor, University of Calgary

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

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 (Estimated)

September 1, 2026

Primary Completion (Estimated)

December 1, 2027

Study Completion (Estimated)

December 1, 2027

Study Registration Dates

First Submitted

July 7, 2026

First Submitted That Met QC Criteria

August 10, 2026

First Posted (Actual)

August 14, 2026

Study Record Updates

Last Update Posted (Actual)

August 14, 2026

Last Update Submitted That Met QC Criteria

August 10, 2026

Last Verified

July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • REB26-0539

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

IPD Plan Description

Aside from eventual publication of study results to help guide practice, we will not be sharing granular study data with other researchers for expansion of the study.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

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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