Is it safe to undergo coolsculpting on the under chin area 7 months after submental lipo?

The first thing that your provider has to asses is if its really fat or skin laxity, because if its the second coolsculpting wont do much and could cause a burn on the area that does not have any fat.

If you are unhappy with the change seen after submental liposuction, you will likely also be unhappy with trying coolsculpting in the area. It sounds like you may have subplatysmal fat present, which will not be improved by coolsculpting. A deep necklift would likely be needed in order to improve things further. I would suggest you see a board certified plastic surgeon with experience in this.