Botox. if injected properly, botox can be used to create a subtle and temporary browlift. Results last 3-4 months. Anecdotally, about 80-85% of patients who have a botox browlift are satisfied.
Muscle relaxation. Botox causes a relaxation of the muscles in the forehead. Some pull the brows in and down while others pull the brow up. The best effect is for the Botox to block a mix of both. When you can not pull the brow in and down they tend to become spread apart and rise up a bit. This is the chemical lift you are talking about. There is also face lifts using Botox and dermal fillers .