METHODS Study 1: Modified human repeat insult patch test to evaluate cumulative irritation and predictive allergy
Men and women aged 18 to 70 years with Fitzpatrick skin type I to IV were enrolled in the study. Individuals were excluded if they had any active or history of skin diseases or conditions that may interfere with the evaluation of skin reactions, had any known allergy to skin care products,or routinely received any anti-inflammatory medications. All participants were required to sign an informed consent agreement consistent with the requirements of 21 Code of Federal Regulations 50.25. This study used a modified human repeat insult patch test developed by Rizer and Nozawa16 that combines cumulative irritation assessment in the induction phase and potential for induction of allergy during the challenge phase. The test protocol is routinely used in Japan and North America for developing product safety dossiers. The test design includes an induction phase and a challenge phase. During the induction phase the test products are applied under occlusive patch 9 times over 3 weeks.