Some stars, like Kim Kardashian, 29, have said they've used Botox. Others insist they haven't. While there appears to be no harm in using Botox early, doctors agree that the body can build up an immunity to the injections, resulting in a less effective product over time. And there's always the danger of having the plan backfire. An overly-Botoxed actor is harder for casting agents to market, which means a few wrinkles might not be such a bad idea after all.