Hyaluronic acid does not get absorbed?

Hyaluronic acid is naturally occurring in your body, so don't be worried about health concerns.  I am not familiar with Stylage as we don't have that available in the US.  Regardless, hyaluronic acid is absorbed by the body over time (some linger longer than others) and a small portion is replaced by collagen that your body creates in response to the product.  If you want to be absolutely sure that it is all gone, you can get your lips injected with hyaluronidase, which would enzymatically eat up the remaining filler particles.  I don't think this is necessary, however.  Enjoy your lips!

All hyaluronic acid fillers eventually get absorbed by the body.  It may take several months for the product to get absorbed and if you are unhappy you can get Vitrase injected to dissolve it faster.

All injected hyaluronic acid is absorbed eventually. Part of the volume enhancing effect of hyaluronic acid is due to the body creating its own collagen in reaction to it. Individuals who achieve long lasting results simply generated more of there own collagen. This is good news for you as you will probably use these agents elsewhere on the face in the future. Since you have such a strong collagen reaction you can anticipated that you will probably have long lasting resuls in the future.  

Hyaluronic acid naturally occurs in the body so there isn't an issue with it being there. You have it in your body anyway and it is what creates volume and youthfulness in the skin. With that being said, Stylage is not a filler we use in the U.S. It is a hyaluronic acid filler, yes, but it also has other ingredients added to it that are supposed to make it last longer and do more for anti-aging. I can't tell you if this is true or not because we don't use it here, but it may be why it is lasting longer for you. "This answer has been solicited without seeing this patient and
cannot be held as true medical advice, but only opinion. Seek in-person
treatment with a trained medical professional for appropriate care."

Hyaluronic acid does eventually get absorbed by the body. Generally HA's last for about a year. So, by now, the hyaluronic acid that was injected into your lips 3 and 4 years ago is long gone. You can have persistent fullness if collagen replaces the HA as it is resorbed. Thank you for your questions. Best wishes.