Botulinum toxin is used to reduce fine lines and wrinkles by paralyzing the underlying muscles. How Long Does a Botox Injection Last? The effects from Botox will last three to six months. As muscle action gradually returns, the lines and wrinkles begin to reappear and need to be treated again. The lines and wrinkles often appear less severe with time because the muscles are shrinking. Do not touch or rub injected site for 2-4 hours following treatment. Avoid exercise and sweating for the remainder of the day and no lying down or leaning forward for 2-4 hours after treatment.