A botox brow lift works in almost any age and depends upon if you have a natural arc going from the inside of your forehead to the outside of your forehead or not. If you have a flat eyebrow which lacks the arc, then Botox would not help, even at age 21. But if you already have it, it is probably a mute point. Premiere Center for Cosmetic Surgery would recommend you see a board certified plastic surgeon to make sure you are guided correctly through your decision. Premiere Center offers complimentary consultations in Miami and in Tampa. Good luck on your decision!