Potassium o-phenylphenate (OPP) is a preservative regulated in Annex V/7 of the Cosmetics Regulation (EC) n. 1223/2009 at a maximum concentration of 0.2% (as phenol). In vitro data indicate an absent or very weak binding affinity of OPP to the oestrogen receptor, in line with limited stimulation of proliferation in oestrogen responsive cells. No information is available on androgenic and anti-androgenic effects of OPP in vitro. Agonistic or antagonistic effects on thyroid hormones were not observed with OPP. There might be a potential of injury to the vision system attributable to OPP. Aggregate exposure to OPP should be considered. OPP and its sodium and potassium salts are used as active ingredients in broad-spectrum fungicides surface biocides. OPP in 2 % [w/v] formulations is used for hygienic hand disinfection and hand decontamination in hospitals and medical practice by professional users. OPP is approved as a preservative in cosmetic formulations according to Commission regulation 1223/2009/EC, its amendments and adaptations. It is listed in Annex V with a maximum authorised concentration of 0.2% without any limitations and requirements, conditions of use and warnings which must be printed on the label. OPP and its sodium salt are also used for inhibition of mould growth on citrus.