Expert consensus on technical specifications of in vitro skin penetration test of cosmetic product

A new consensus by a team of experts in China has been established to guide researchers in evaluating the percutaneous absorption of cosmetic functional ingredients using in vitro diffusion cell technology. This approach simulates the skin’s transdermal absorption process, offering insights into how cosmetic ingredients interact with different skin structures and their efficacy in topical formulations.

Cosmetic products are designed to deliver functional ingredients to the skin surface, where they may act either on the surface or penetrate deeper to reach targeted sites. The efficacy of these products depends heavily on the diffusion and penetration properties of the ingredients.

This consensus aims to bridge the gap in testing standards for cosmetic ingredients to improve safety and efficacy for consumers.

Key highlights

Importance of skin penetration studies: Research into the penetration, intradermal retention and potential systemic absorption of cosmetic ingredients plays a critical role in guiding formulation development, efficacy assessment and safety verification.

Diffusion cell technology: The diffusion cell test is a widely used in vitro model that replicates the skin’s transdermal absorption process. This technology allows researchers to evaluate the distribution and absorption of cosmetic ingredients across various skin structures. Results from these tests provide valuable references for formulation adjustments and serve as an effective ex vivo method for studying topical dosage forms.

Lack of standardized guidelines: While the PRC State Administration of Quality Supervision and Quarantine has established guidelines for the in vitro testing of drug molecule absorption, similar standardized methods for cosmetic components have been lacking. The complexity of experimental conditions and influencing factors presents significant challenges in standardizing these tests.

Recommendations: The new consensus, published in the Journal of Dermatologic Science and Cosmetic Technology, provides technical recommendations for conducting percutaneous permeation tests using in vitro diffusion cells. Key goals include reducing variability across studies and ensuring reliable evaluation of ingredient functionality.

The consensus acknowledges that cosmetic formulations with varying compositions may exhibit different release kinetics.

Researchers are encouraged to tailor study designs to their objectives, guided by national regulatory principles and the specific properties of the functional ingredients under investigation.

Recognizing the limitations of current expertise and the rapid advancement of related technologies, the consensus will be updated periodically to reflect new developments in the field.

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Contact author details: Qi Xiang, College of Life Science and Technology, Jinan University, Guangzhou, China, txiangqi@jnu.edu.cn

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