If they are glazed ceramic tiles, they are not porous and do not require sealing. If they are unglazed ceramic tiles, they do need to be sealed. In both cases, we recommend that you seal the grout lines between the tiles. Use either the Premium Sealant or Tile & Grout Sealant. Any application to the surrounding glazed ceramic tiles is not a problem as MR Seal dries invisible. It will also help keep the tiles cleaner for easier maintenance.