Primary irritation index and safety zone of cosmetics: retrospective analysis of skin patch tests in 7440 Korean women during 12 years

BackgroundCosmetics are products used over long periods by the public, and their safety is very important. Several types of human tests are used widely for the evaluation of cosmetics including single patch tests, in-use tests, human repeated insult patch test (HRIPT). However, there is no clear and well-defined published objective and standardized criteria for primary skin irritation in regard to the large variety of cosmetic products. MethodsThis study analysed human patch tests conducted from May 2001 to December 2012 with 4606 materials of prototype or finished cosmetic products on 7440 normal Korean women aged 18-60years. The tested products were patched under occlusion for 24 or 48h, and skin tolerance was assessed twice at 30min and 24h after patch removal using a 5-step scale according to the CTFA guidelines. ResultsHuman patch tests for cosmetics were performed of 4606 cases, and 30-33 subjects participated in each case. The response in each case was calculated based on total subject number, skin reaction intensity and the number of respondents. The calculated response was standardized using the z-score, and a safety zone was provided in terms of human primary irritation in accordance with the human skin reaction evaluation criteria and usage or formula of cosmetics. ConclusionsThis study established the safety criteria for irritation in the cosmetics field.