Conclusion of the opinion: 1. In view of the above, and taking into account the scientific data provided, does the SCCS consider the nanomaterials Gold and Colloidal Gold, Gold Thioethylamino Hyaluronic Acid and Acetyl heptapeptide-9 Colloidal gold are safe when used in leave-on skin cosmetic products according to the maximum concentrations and specifications, taking into account reasonably foreseeable exposure conditions? The SCCS has considered all the information provided by the Notifiers and is of the opinion that it is not possible to carry out safety assessment of the nanomaterials (Gold, Colloidal Gold and Surface Modified Gold) due to limited or missing essential information. Much of the information provided on toxicity relates to gold as such, and it is not possible to determine the relevance of the data for nano-forms of any of the materials under the current evaluation due to the absence of full study reports. Detailed data and information need to be provided on physicochemical characterisation and toxicological evaluation, along with experiment performance to allow safety assessment of the nanomaterials. In regard to surface modified gold, all notifications relating to Acetyl heptapeptide-9 Colloidal gold (nano) were withdrawn by the Notifiers and therefore only Gold Thioethylamino Hyaluronic Acid has been considered in this Opinion. 2. Does the SCCS have any further scientific concerns with regard to the use of materials A, B and C in nano form in cosmetic products? The information obtained from scientific literature suggests possible systemic uptake of gold nanoparticles which may lead to accumulation in certain organs - notably the liver and spleen. In addition, the available data from literature indicate potential mutagenic/genotoxic effects of gold nanomaterials. These indications raise an alert that warrants further safety evaluation of gold nanomaterials when used as cosmetic ingredients. In the absence of sufficient data to allow safety assessment, the SCCS has considered these aspects and has concluded that there is a basis for concern that the use of Gold (nano), Colloidal Gold (nano) and Surface Modified Gold (nano) materials in cosmetic products can pose a risk to the consumer. The SCCS concerns for consumer safety in this regard are detailed in Annex II. The SCCS will be ready to assess any evidence provided to support safe use of the materials in cosmetic products. Opinion to be cited as: SCCS (Scientific Committee on Consumer Safety), Opinion on Gold (nano), Colloidal Gold (nano), Gold Thioethylamino Hyaluronic Acid (nano) and Acetyl heptapeptide-9 Colloidal gold (nano), 30/31 March 2021, SCCS/1629/2021.