Percutaneous Absorption of Sunscreen Filters: Review of Issues and Challenges.

Although skin is a vital barrier to the outside world, it is permeable to certain substances used in topical pharmacotherapy. It is therefore not surprising that other xenobiotics intentionally or accidentally coming in contact with skin can cross the skin barrier. Long before the turn of the millennium, it became clear that sunscreen filters from sunscreen products can be systemically absorbed and detected in urine and plasma. Against this background, we review issues and challenges with safety assessments related to the possible percutaneous absorption of the sunscreen filters. A reference is made to the Regulation (EC) No. 1223/2009 of the European Parliament and of the Council of 30 November 2009 on cosmetic products (version 1 August 2018) and the concepts of the Maximal Usage Trial (MUsT) and Generally Recognized As Safe and Effective (GRASE), currently discussed in the United States.