Silicones tend to be “filler” and don’t contribute much to product efficacy. Further, for acne-prone people, silicones can act as a ‘barrier’ and trap oil, dirt, and dead skin cells, making acne worse. They are also bio accumulative: once they’re rinsed down the drain, they contribute to the build-up of pollution in oceans and waterways and may not break down for hundreds of years.