Researchers in Thailand are conducting a pilot clinical trial to evaluate the potential for skin irritation and sensitisation from a turmeric and epigallocatechin-3-gallate emulgel.

The randomized, double-blind study uses a validated patch testing protocol to assess the topical product’s safety before future testing in patients with inflammatory skin diseases. The findings will inform the design of larger-scale clinical trials.

The study enrolled 60 healthy Thai men and women aged 20 to 60 years with Fitzpatrick skin phototypes III and IV. Participants were excluded if they had a history of dermatologic conditions, recent vaccinations, or had taken medications that could affect immune or skin responses.

A sample size of 60 was selected to account for a 20% dropout rate and to ensure at least 50 participants completed the protocol. This provided a 92.3% probability of detecting at least one sensitisation response, based on an estimated 5% occurrence rate.

Participants received topical applications of four products: turmeric/epigallocatechin-3-gallate (EGCG) emulgel at 0.12% and 0.24%, a blank emulgel vehicle, and a normal saline solution as control. Each was applied via occlusive adhesive patches to the upper back in a randomized sequence.

The 6-week study included:

• Induction phase (weeks 1–3): nine patch applications, assessed for irritation

• Rest phase (weeks 4–5): no intervention

• Challenge phase (week 6): a single patch on a naïve skin site, assessed for sensitization

Irritation was measured using the Draize scoring system. Sensitisation was evaluated 30 minutes and 48 hours after patch removal using the International Contact Dermatitis Research Group (ICDRG) criteria. A trained, blinded evaluator conducted all assessments.

Results are pending. Irritation scores were collected after each application. A Cumulative Irritation Index (CII) was calculated for each participant, and the Mean CII (MCII) determined the irritancy level of each formulation.

Sensitisation was classified using ICDRG guidelines, with patients who showed a score of "+" or higher being assessed for potential sensitisation. Participants who showed a Draize score ≥2 at any site had testing relocated. If the same reaction occurred again, patch applications were discontinued for that individual.

The pilot study is limited by its small sample size and demographic homogeneity. Only participants with Fitzpatrick skin phototypes III and IV were included, limiting applicability to individuals with lighter or darker skin tones.

Patients with existing dermatologic conditions were excluded, which may limit the relevance of results for the target patient population.

“The primary objective of this study is to evaluate the skin irritation and sensitisation potential caused by the turmeric/EGCG emulgel, compared with a normal saline solution, in healthy Thai volunteers. The secondary objective is to assess its overall adverse effects in the same group,” said Kankanit Yeerong from Clinical Research Center for Food and Herbal Product Trials and Development (CR-FAH), Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand, and colleagues.

If no significant irritation or sensitisation is observed, the findings will support advancement to larger efficacy trials in patients with inflammatory skin diseases.

The data will also assist in meeting regulatory safety requirements for future herbal-based topical therapies.

The authors reported no conflicts of interest.

Source: BMJ Open