What Is Filler Migration?
Migration means the product has ended up outside the place it was put.
Defining it is easy — the work is in separating the real thing from three conditions that get called by its name, because the word has expanded online until it covers almost any filler result somebody dislikes.
Three things it isn't
Swelling. For a fortnight after treatment, and especially in lips, the tissue is holding water alongside gel. A ledge above the lip on day four is oedema. Judge nothing before two weeks.
Too much product. A lip that looks oversized is a quantity decision. The gel is precisely where it was placed; there's simply more of it than the structure wanted.
Stacking. Residual product from earlier rounds gets added to, and the combined result spreads wider than either round would have alone. From the outside it looks identical to migration. It isn't, and the fix is different.
The genuine article looks like a defined ridge or fullness sitting just outside the treated boundary. In lips, that's a shelf above the vermilion border throwing a shadow that wasn't there before you started.
What causes it
Start with the plane, because it's the most important and least discussed. Gel placed deep, in a stable compartment, is held there by the surrounding architecture. Gel placed close to the surface is in a mobile layer that gets compressed and displaced thousands of times a day, and it travels.
Then quantity. Tissue has a capacity, and past that capacity product goes wherever the resistance is lowest. This is the commonest single contributor.
Then frequency. Returning before the last round has meaningfully resolved compounds the volume problem, and because each addition is small it happens without anyone noticing a decision being made.
Then product choice. A soft, spreadable gel used where structure was required behaves exactly as you'd expect a soft, spreadable gel to behave.
And finally movement. Lips and the perioral area account for most of the cases people write in about, for the obvious reason that they never stop moving.
A word in the injectors' defence. Some settling is normal, expected and invisible. Keeping product perfectly bounded in the most mobile part of the face for a full year is a real skill rather than a baseline expectation, and "something moved slightly" is not the same complaint as "there's a ridge in the wrong place".
Telling, and then acting
Wait the full two weeks. Most of what gets posted online as migration on day three is water.
Then look in flat, even light with your face relaxed. Real migration has a boundary you can see and often one you can feel. Compare against a photograph taken before treatment, which is the main reason to have taken one.
If you think something has moved, return to the person who placed it. That isn't a confrontation, it's the next appointment, and any experienced injector would far rather see it in the room than read about it online.
For hyaluronic acid products the tool is hyaluronidase, which dissolves the gel in the treated area. It's a quick procedure, almost always billed separately, and most injectors will make you wait a while before placing anything fresh. The area will look deflated and slightly strange for a few weeks. That resolves.
If what you had wasn't hyaluronic acid, dissolving isn't available. That single fact is the strongest argument for sticking to hyaluronic acid products until you know how your face responds to them.
Keeping it from happening
Go slowly and build in small increments. The people who end up here are almost never the ones who had a modest amount placed carefully on one occasion.
Space appointments properly, and ask how much residual product your injector believes is still present before adding to it. Be wary of any plan that tops you up on a fixed calendar without an assessment attached.
Talk about placement rather than volume. An injector who discusses structure and support, and who is willing to say that today the answer is no, is the one you want.
And ask what they'd do if it migrated. The answer should arrive immediately and be specific.
One practical note on timing. The deflated fortnight after dissolving is real, so don't schedule it against anything you care about. If you want to read the literature on placement planes and gel rheology rather than take a summary, a college library such as the one at Hudson County Community College opens the databases. And if the recovery window involves being outdoors, forecast pages from the National Weather Service beat guessing.