What age you are when you start to get lines and wrinkles is a bit of a “How long is a piece of string?” question; everyone’s skin ages at different rates and it depends on your skin type, race, genetics, and lifestyle. Dr. Townshend says, “I see some ladies who are 23, 25, and they’ve been smoking for 10 years and using sun beds, so they’re very different [from] somebody who’s 35 who’s looked after themselves.”“You have to treat what you see in front of you, not the patient’s age,” says Dr. Sarah Tonks, from Omniya clinic in Knightsbridge, U.K. She says that if you have a “hyper-mobile” face (that’s lots of smiling, frowning, raised eyebrows, and WTF faces), she’d consider treatment in the 20s to stave off lines and wrinkles. “But if they...don’t have hyper-mobile muscles, then there’s no point in doing it,” she adds.Dr. Jonquille Chantrey, who runs Expert Aesthetics in Cheshire, U.K., agrees that she’d treat someone with a hyper-mobile face with Botox earlier — earliest she says is around 28 — but she also believes that your expression lines are part of who you are, and not necessarily something you should try to hide.“It depends on where on the face the lines are. If they’re part of the person, like an attractive part of their expression, then I usually say to leave it a little bit longer,” she says. “And for me, I don’t think that smile lines are a particularly negative thing, if those other factors have been considered and managed.”Does getting started too early actually make things worse in the long run? Dr. Zamani says yes. She says paralyzing the muscles in your brow or around your eyes will, over time, cause them to atrophy (that’s the medical term for when a muscle withers from underuse — think what an arm looks like when you have a cast removed after a broken bone). Smaller facial muscles mean less volume in the complexion, which is another sign of skin aging.Dr. Townshend doesn’t think that’s a reasonable argument, though, partly because the muscles in the face are so tiny that if they do shrink a bit, no one’s going to notice. “I don’t buy into this idea that I could walk down the street and say, ‘That lady’s got an atrophied forehead,’” he says.However, Dr. Chantrey says she’s seeing problems with younger patients who’ve had their foreheads over-injected. “What I’m seeing is their brows are starting to drop earlier than would be normal for them. If you’re overly injecting [the horizontal forehead lines], it compromises the brow position, so it does give you a slight brow heaviness, potentially.”A similar problem could occur if you have too much Botox injected around the crow’s feet too young. “If the smile lines are treated aggressively too early, it can flatten off the sides of the eyes; it can give a more unnatural smile,” she says. And although the effects of too much, too young are reversible, Dr. Chantrey says it can take time — longer than the three to four months it takes for your Botox to wear off.There are, of course, other ways you can “service” — to use Dr. Townshend’s terminology — your face in your 20s without injectables. A good skin-care regime that’s high in antioxidants like vitamins A and C, plus daily SPF, is a starting point — and topical treatments like peels that are rich in alpha-hydroxy acids can help reduce the appearance of early fine lines.No one needs to get Botox. If you choose to have a little work done to smooth out some lines, great. If you don't, great. But when it comes to getting it done early in life, there’s more to consider than just the cost.