Dermatologists often say that Botox—or any injectable neuromodulator that softens lines, for that matter—is just as much an art as it is a science. And just as there’s no one “right” approach to smoothing out wrinkles, there’s no “right” age to get started with injectables. However, depending on the decade when you decide to get your first treatment, your experience might vary a bit. So we chatted with dermatologists to help you understand what to expect at every age.

“Botox [(and similar injectables like Dysport, Xeomin, and Jeuveau)] works by preventing dynamic wrinkles by temporarily weakening the underlying muscle,” says Dendy Engelman, MD, a board-certified dermatologist in New York City, previously told Well+Good. Dynamic wrinkles are those caused by the movement of the underlying muscle, which occur when you make facial expressions. Over time, these etch into your skin, and turn into a static line that’s visible even when your face is at rest. “With Botox treatment, the muscle contraction is weakened and the overlying dynamic wrinkle is lessened. And with early and effective treatment, it can not only reduce the dynamic lines with movement but soften or eliminate static lines as well,” she says.

But how early is too early might be the question that pops into your mind. “A very common question is: ‘What’s the right age to start?’” says Carolyn Treasure, MD, the co-founder of Peachy, an injectables studio in New York City. “People wonder if they should have started earlier or if they’re starting too late, but there’s not one specific age for everyone.” The question of “when,” she says, really depends on the stage of your wrinkles, and how deeply they’ve etched into your face. “It’s really when you have dynamic lines that are just starting to progress or about to progress to static lines.”

That said, the progression of those wrinkles does correlate, at least to some extent, with how old you are, because of the changes your skin undergoes as you get older. Your skin’s natural production of collagen and elastin slows down around the time you hit 30, and factors like sun exposure and lifestyle habits like smoking, your diet, and stress levels can all play a role. With that in mind, read on for what you can—and can’t—expect from Botox at every decade.

In your 20s

In your 20s, Botox is used largely for preventative purposes. At this point, wrinkles are considered “stage one,” which means that they show up when you make an angry face or furrow your brow, and stick around for only a brief amount of time before disappearing completely. “There’s a little bit of a misunderstanding about what ‘preventative Botox’ is,” says Sarmela Sunder, MD, a double-board-certified plastic surgeon based in Los Angeles. “A lot of people think that they’ll put Botox in their forehead and lines will never develop there, but that’s not it. If the lines aren’t there, you don’t need Botox, but if lines show up when you make a face and show up for a few seconds or minutes afterwards, that’s where you’re going to start developing permanent creases in the skin architecture, so you want to start doing Botox at that point to prevent those lines from laying down.”

Usually, these dynamic wrinkles first appear on your forehead, between your eyebrows, and around your eyes. “Preventative Botox keeps those lines from being etched in, and softens any wrinkles that are already there,” says Sheila Farhang, MD, a board-certified dermatologist and the founder of Avant Dermatology in Arizona. “People who start early and do a little bit won’t need as much later, because they won’t have those muscles that they need to really freeze, or they can stretch it out longer in between treatments because the wrinkles aren’t as visible. However, if you don’t have any of those movement-induced wrinkles yet, any good dermatologist will turn you away, because you’re not at the point when it can really do anything yet. “I have 20 year-olds who come in for Botox, and I have to tell them that it’s not right for them at this time,” says Dr. Farhang.

In your 30s

According to Dr. Treasure, most patients come in around the time they’re in their late 20s and early 30s. This is the time when the natural production of collagen and elastin starts to slow down, and their dynamic wrinkles start to progress toward static or “stage two” lines. While the stage one dynamic wrinkles only appear when your face is moving, these stage two static wrinkles are always around, even when your face is at rest. “Usually it’s in their 30s when people start to see fine lines,” says Dr. Farhang. She explains that the amount of Botox you get tends to (coincidentally) correspond with your age. “Someone who is in their 20s or 30s is usually getting 25 to 35 units, or what we call ‘Baby Botox,’ and then we go up from there,” she says.

It’s worth noting that the amount of Botox you get also depends on the strength of the muscle in a given area. So someone may get more units if they have a stronger brow and still have a subtle effect (leave this part up to your dermatologist, who knows best). But by and large, the number of units you get helps to dictate how long you’ll see the injectable’s effects. “The greater the number of units, the longer the product will last,” says Dr. Sunder. “The fewer wrinkles you have, the fewer number of units you do, and for that reason it doesn’t last as long. However, because the lines aren’t as deep, you may not notice them as quickly when the Botox starts wearing off as you would with later-stage wrinkles.”

In your 40s

If a wrinkle has set firmly into your skin, to the point where makeup starts to get caught in it, it’s considered “stage three.” At this point, says Dr. Sunder, Botox is used more as a treatment than as a prevention, and can help to soften lines that are already there but can’t get rid of them entirely. “For someone who has stage three lines, when the Botox starts wearing off you’ll start seeing the lines sooner even though the Botox is still there,” says Dr. Sunder. “It becomes more obvious because the lines are deeper, so when they come back at 50 percent, it’s more visible than they would be if they weren’t as deep to begin with.”

In your 50s and beyond

When your wrinkles progress to “stage four,” which is characterized by deeply etched lines, “there’s only so much Botox can do,” says Dr. Sunder. “Botox can soften the muscle movement, so it can keep those lines from getting deeper, but once it’s deeply etched in it’s not really going to reverse the lines that have already formed to any significant extent,” she says. If you want to truly get rid of the lines, you’ll need to supplement Botox with a secondary treatment, like lasers, microneedling, or an intense peel. “Botox will still be helpful because…it will prevent them [lines] from getting even deeper, but you’ll need to do another treatment to make sure they actually go away,” says Dr. Sunder.

Other considerations

One thing to keep in mind is that starting Botox early can be a double-edged sword. On the one hand, it can prevent wrinkles from forming into your face, which means that when it wears off you won’t be able to see them as clearly as if you’d never gotten Botox at all. But on the other? “If you do a lot of Botox, your body can get used to it and it might not work as well,” says Dr. Farhang. “And you might need more, or sometimes we’ll use other neurotoxins like Dysport or Xeomin [to give better results].”

While there’s never a point that it’s “too late” for Botox, your lines may reach a point where other treatments may be beneficial. “If you have etched lines or are noticing lines really starting to form, you really have to be careful because at some point Botox is not going to help,” says Dr. Farhang. All of that said, when—and if—you decide to treat your wrinkles with injections is entirely up to you. And now, you’re armed with the knowledge to make that choice in the most educated way possible.

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