Different from hyaluronic acid or collagen protein injection,which are both physical filling. The mechanism of action occurs through the stimulation of fibroblasts in response to a subclinical tissular inflammation.It is this fibroplasia that produces the desired cosmetic result. New collagen begins to form after one month and continues to increase for nine months to a year. In the sixth month, many PLLA microspheres become porous and surrounded by macrophages. After this period there is no evidence of fibrosis and the PLLA particles disappear. The product's degradation occurs through non-enzymatic hydrolysis into lactic acid monomers that are metabolized into CO2, H2O or incorporated into glucose. With its half-life estimated at 31 days, PLLA is totally eliminated from the body in about 18 months. The effect can be seen after injection for 2-3 weeks. However, the duration effect can be as long as 24 months or above. It is suitable for increasing the volume of depressed areas, particularly to correct skin depressions, such as in skin creases, wrinkles, folds, scars and for skin aging. Injectable PLLA is also suitable for large volume corrections of the signs of facial fat loss (lipoatrophy).