Cyclomethicone 5 (D5) is a clear, alcohol-free and odorless liquid, added to personal skin care products to give them a smoother texture that is more easily applied to the skin. Cyclomethicone 5 is member of cyclomethicone, which are a group of liquid methyl siloxanes that have low viscosity and high volatility. Because molecules of this chemical are too large to enter human pores, and don’t tend to block the active ingredients from entering the skin, cyclomethicone is a commonly used as a skin emollient ingredient. Cyclomethicone 5 can cause minor skin and eye irritation. Some DNA damage has been reported in mouse lymphoma cell assays, and uterine carcinogenicity of Cyclomethicone 5 reported in rats after long‐term exposure. Reduced levels of mRNAs for other DNA repair proteins in human breast epithelial cells were also observed after exposure to Cyclomethicone 5. Cyclomethicone 5 has been defined as a very persistent very bioaccumulative (vPvB) substance of environmental concern, which has led to the submission of a proposal for their restriction in Europe.