Botox can be used in patients of any age. It really depends on the indication. Botox can be used to treat multiple disorders, including cerebral palsy, and many young children are treated with Botox for that indication. When Botox is used for cosmetic indications, the doctor and patient need to determine if there is a real indication for it's use. Given the prevalence of crows feet, forehead wrinkles, and frown lines, its use is steadily increasing. Many patients understand that using Botox at a younger age (20s) can be preventative and therefore start Botox at an earlier age. In rare cases, it might be necessarily to use Botox for a cosmetic indication in a patient in their late teens, but this would be very rare.