
The argument for starting Botox early rests on a distinction worth understanding before you decide either way.
A dynamic line appears when the muscle contracts and disappears when it relaxes. Across years of repetition, skin folded in the same place loses the ability to spring back, and the line becomes visible at rest. That is a static line, and it is a different problem.
Static lines live in the skin. Treating them means resurfacing, or filler, or both. Dynamic lines answer to a neuromodulator.
If a static line forms because a dynamic one repeated often enough, reducing the repetition should slow that progression. That is the reasoning behind preventative treatment and it is sound. Patients who start in their late twenties or thirties are generally maintaining smooth skin rather than trying to recover it.
What is less certain is the specifics. You will see it claimed that early treatment means fewer units later. That may hold for some patients and it is not well established. Treat it as a plausible benefit rather than a promise.
Not immobility. Dosing for prevention is lighter than dosing for correction, and the aim is to soften the strongest movements while leaving your expression intact.
Not universal. There is no age at which everyone should start. It depends on how strong your muscles are, how your skin behaves, and whether lines are appearing at rest yet. Some patients in their thirties do not need it. Some in their late twenties do.
Ask a provider to show you which of your lines are dynamic and which are already static. That is a two-minute assessment in front of a mirror, and it will tell you more about whether to start than any general guidance can.