The goal of this clinical trial is to assess whether a medical-grade Norway spruce resin-based topical product (Abilar) causes skin irritation or allergic sensitization in healthy adult volunteers. The main questions it aims to answer are:

Does the product cause skin irritation after repeated applications? Does the product induce sensitization (allergic contact dermatitis) after repeated exposure?

Participants will:

Have the test product applied to their skin via occlusive patches multiple times over three weeks.

Undergo dermatological assessments for signs of erythema (redness), swelling, or sensitization at scheduled time points.

Have a final challenge application on a new skin site after a rest period to check for delayed allergic reactions.

This study follows Good Clinical Practice (GCP) guidelines and the Declaration of Helsinki. It was conducted at Princeton Consumer Research (PCR Corp, UK) with approval from the East Anglia Ethics Committee, UK.

Study Objective:

This is a single-center, interventional study designed to evaluate the irritation and sensitization potential of a medical-grade Norway spruce resin-based wound care product (Abilar) using a Modified Draize Human Repeat Insult Patch Test (HRIPT). The study followed Good Clinical Practice (ICH GCP 1996) and the Declaration of Helsinki.

Study Design:

A total of 215 healthy adult volunteers were enrolled, with 207 completing the study. The study was conducted at Princeton Consumer Research (PCR Corp, UK) and was approved by the East Anglia Ethics Committee, UK. Participants received occlusive patches containing the test product, applied repeatedly over a three-week induction phase. After a rest period, a challenge application was placed on a new skin site to evaluate potential delayed-type hypersensitivity reactions.

Single-center, interventional study with single-group assignment (no control group).

Conducted under dermatological supervision at Princeton Consumer Research (PCR Corp, UK).

Ethical approval was granted by the East Anglia Ethics Committee, UK. Study Period: October 16, 2019 - October 25, 2019.

Methodology:

Induction Phase (Days 1-21): Repeated application of occlusive patches with the test product to the same skin site three times per week. Skin assessments were conducted at multiple time points.

Rest Period: No patch application for approximately 14 days. Challenge Phase (Day 38): A final application was made to a naïve skin site to assess delayed hypersensitivity responses.

Scoring System: Skin reactions were graded using dermatological visual scoring for erythema, edema, and other signs of irritation or sensitization.

Inclusion Criteria:

• Healthy volunteers, of either sex, aged at least 18 years.
• Completed written informed consent.

Exclusion Criteria:

• Pregnancy or lactation.
• Inadequate or non-existent contraception (women of child bearing potential only).
• A current skin disease of any type apart from mild facial acne (e.g. eczema, psoriasis).
• Heavy alcohol consumption (i.e. more than 21 units per week or 8 units a day for men, more than 14 units per week or 4 units a day for women).
• Current use or history of repeated use of street drugs.
• A febrile illness lasting more than 24 hours in the six days prior to first patch application.
• Significant past medical history of hepatic, renal, cardiac, pulmonary, digestive, haematological, neurological, locomotor or psychiatric disease.
• History of asthma only if requiring regular medication or hay fever that required prescription treatment in two or more of the previous three years.
• A history of multiple drug hypersensitivity.
• Concurrent medication likely to affect the response to the test articles or confuse the results of the study.
• Known sensitivity to the test articles or their constituents including patch materials.
• Current treatment by a physician for allergy unless physician consulted by Investigator and participation approved.
• Participation in a repeat insult patch test (RIPT) or follow-up work within the last month.
• Sensitisation or questionable sensitisation in a RIPT.
• Recent immunisation (less than 10 days prior to test patch application).
• A medical history indicating atopy.

Prohibitions and Restrictions:

• No use of aspirin or non-steroidal anti-inflammatory drugs for the duration of the study.
• No use of sun beds or sun lamps and no deliberate exposure of the test sites to natural sunlight for the duration of the study.
• No immunisation from ten days prior to first patching until study completion.

Individual participant data (IPD) collected throughout the study, including anonymized participant-level skin reaction assessments, will be made available upon request for research purposes.

Data will be available upon request after study completion and final publication, with an access period of 5 years post-publication.

Researchers requesting access to anonymized IPD must submit a written request outlining the intended research objectives. Data access will be granted following review and approval by the sponsor (Repolar Pharmaceuticals Oy) and compliance with data protection regulations.

This study was conducted as a single-blind HRIPT, where participants were not informed of the identity of the test article applied to their skin. However, as only one test product was used without a control or comparison group, ClinicalTrials.gov does not allow classification as "Single-Blind," and the study is categorized as "Open Label" in this registration.