A lip flip helps people achieve a fuller upper lip without the use of dermal fillers. (They only work on people whose lip curls under when smiling.) Here’s how it works: Botox injections are used to temporarily relax the muscles around your mouth. This stops the top lip from curling under when you smile. There is no downtime, but it might feel a little weird at first when you drink through a straw or whistle! Results take 2 weeks to set in and last for about 8 weeks.