C11-15 Sec-Pareth-12 is a cleaning agent, or "surfactant", that can be found in a variety of cosmetic and personal care products. We use it in our products to remove dirt and deposits by surrounding dirt particles to loosen them from the surface they're attached to, so they can be rinsed away. It can also be used as an emulsifier. It ensures that our products provide the same performance use after use. Over time, it is possible for formulas in a product to separate. An emulsifier helps oil mix into the water.