What matters most about this question is the components that make up the pad. Most rug backing with anti-slip qualities contain a form of rubber or latex (whether synthetic or natural) that can lead to stains and/or dis-colorization from contact. A good majority of rugs out there in the industry will not have rubberized backing. But to make sure, always read or feel the rug on the back to make sure what the backing is. If you decide to purchase one online, always read the specifications to ensure it doesn’t have a rubber backing.