Cyclopentasiloxane is a type of silicone that is used in skin care products as a conditioner, lubricant and solvent. Its watery consistency makes it easily spreadable. It adds a silky, slippery feeling to products and also and acts a mild water repellent by forming a protective barrier on the skin. In anti-aging formulas, it can also fill in some of the fine lines and wrinkles (think drywall filler) giving the face a more plump look — albeit temporary. The ‘slippery’ characteristic makes a great addition to hair products, especially conditioners. It also evaporates quickly, which makes it ideal for helping to deliver other ingredients to the skin and hair in products such as hand lotion and foundation. Cyclopentasiloxane may cause mild skin and eye irritation and a small percentage of it seems to penetrate the skin. While it isn’t toxic to the human body, there are concerns about its environmental impact. More research is being done.