L. D’Souza, R. Patel, H. Varga, and C. Morley
Correspondence: The StemX Research Group, SXR Laboratories
Full Article
The StemX Research Group, SXR Laboratories
Date: 7 September 2025
Contributors: L. D’Souza, H. Varga, R. Patel, and C. Morley
Contact: research@sxrlabs.com
Abstract
This internal evaluation examined the performance of a modified patch testing protocol designed to reduce background irritation during contact allergen testing in adults with mild contact dermatitis. The revised procedure incorporated shorter occlusion time (24 h vs. 48 h) and reduced allergen concentration for selected preservatives and metals. Thirty-six participants were tested under NHS governance and Health Research Authority approval. The modified approach yielded comparable detection rates with a 28% reduction in mild irritant reactions. These findings support further assessment of reduced-load patch testing protocols within UK dermatology outpatient services.
1. Introduction
Patch testing remains the standard diagnostic procedure for allergic contact dermatitis but can produce false-positive results due to non-specific irritation. Traditional 48-hour occlusion protocols are well validated but often poorly tolerated by patients with mild or subacute dermatitis. This evaluation sought to determine whether a reduced occlusion and allergen-load protocol could maintain diagnostic sensitivity while improving patient comfort and clinic efficiency. The project was conducted within an NHS Trust dermatology service under HRA and local REC approval (Ref: 25/LO/0108), compliant with MHRA non-CTIMP research guidance.
2. Methods
Study design: Prospective, within-subject comparison of standard versus modified patch test panels conducted between May and August 2025 at the SXR Clinical Research Unit, London.
Governance: The study was approved by the Trust R&D department as a service evaluation and registered with the Health Research Authority (HRA). All activities followed UK Good Clinical Practice (GCP) for non-investigational procedures and adhered to UK GDPR for pseudonymised data.
Participants: Thirty-six adults (22 female, 14 male; mean age 42.9 ± 11.3 years) with clinically suspected mild allergic contact dermatitis.
Procedures:
- Each participant received two adjacent series of standard allergens (European baseline series).
- Standard protocol: 48-hour occlusion at full concentration.
- Modified protocol: 24-hour occlusion with 50% concentration for formaldehyde, methylisothiazolinone, and nickel sulphate.
- Readings were taken at 48 h and 96 h by two independent dermatology clinicians blinded to protocol type.
Outcomes:
- Concordance of positive allergen reactions between protocols.
- Frequency of mild irritant or doubtful reactions.
- Participant-reported discomfort scores (0–10 scale).
Statistical analysis: McNemar’s test for paired proportions and Wilcoxon signed-rank test for discomfort scores were applied using SPSS v28. Significance was defined as p < 0.05.
3. Results
Concordance between protocols was high (κ = 0.88). Positive reactions were observed in 19 participants (53%) under the standard method and 18 (50%) under the modified protocol (p = 0.82). Irritant or doubtful reactions decreased from 14% to 10% of all test sites (−28%, p = 0.04). Mean discomfort scores improved modestly (3.8 → 2.9, p = 0.02). No severe reactions were recorded, and patch adhesion remained adequate at 24 hours.
4. Discussion
The reduced-load protocol achieved near-identical diagnostic yield with fewer irritant responses and improved tolerability. Although small, the sample supports the feasibility of implementing shorter occlusion times for selected allergens in UK outpatient settings.
Clinicians noted that the 24-hour removal time simplified scheduling and improved adherence to appointment windows, reducing weekend review demand. The study highlights that minor procedural refinements can deliver measurable service benefits within NHS and MHRA governance frameworks, without altering the regulatory classification of the materials used.
5. Limitations
- Single-centre study with limited participant numbers.
- Restricted to a subset of common allergens; broader panels were not tested.
- Evaluation focused on immediate outcomes; long-term reproducibility unassessed.
- Potential observer bias despite blinding due to visible patch edges.
6. Conclusion
A 24-hour, reduced-concentration patch testing protocol demonstrated comparable diagnostic accuracy with lower irritation rates in adults with mild contact dermatitis. While modest, these findings support cautious adoption of simplified methods in selected patients, provided procedures remain under local dermatology governance and quality assurance systems. Further multicentre evaluation is warranted before national standardisation.
7. References
StemX Research Group. Internal Dermatology Methods Report SXR-DERM-2025-06. 2025.
British Association of Dermatologists. Guidelines for Diagnostic Patch Testing. London: BAD; 2023.
Health Research Authority. UK Policy Framework for Health and Social Care Research. London; 2024.
MHRA. Good Laboratory and Clinical Practice for Non-Investigational Studies. London; 2025.
NICE NG190. Managing Contact Dermatitis. London; 2023.