Crosslinking Restylane Kysse with BDDE, a component that contributes to the formation of a network of HA, results in a gel filler that lasts for a longer period of time. Fillers that contain HA, such as Restylane Kysse, have HA that has been engineered to remain in the body for a longer period of time than the HA that occurs through natural processes. For the purpose of alleviating discomfort during injections, Restylane Kysse contains 0.3% lidocaine.