After the advent of collagen in the ’80s, the second revolution in the use of new material was the hyaluronic acid, in the ’80s and ’90s. There is not such a used material of these past years as hyaluronic acid, and the treatment done with this material are millions all around the world. It is a natural substance of the body that can be injected under the wrinkles to improve them. Besides boasting an important volumetric effect, it always allows a revitalization of the treated zone with a stimulus for the formation of collagen and elastin. It is a completely reabsorbable product and it is one of the safest on the market, especially the last that came out, because it is more purified and with the process of reticulation (the process that allows the acid not to be reabsorbed in a short time) is more and more innocuous. About this we need to remember that completely safe products do not exist: even water or injectable antibiotics can provoke problems. And even the hyaluronic acid in very rare cases can generate intolerances. It has to be highlighted that while for other reabsorbable fillers (collagen and agarose) there are not a lot of products on market and everyone’s responds to well-documented criteria of safety and provenance, this is not always true for hyaluronic acid. Every year, to our congresses, we find new more and more cheap materials, without knowing where they come from. This aspect is one of those that determine the price of the session. As I always said, you have to distrust those very low cost materials that can hide low safety. In these cases, in my opinion, it is not worthy to save money. Basically it deals with pre fulfilled syringes with a gel that is injected in determined facial points to improve wrinkles, furrows or increase the volumes of determined zones, as lips or cheekbones. I have executed these implants for many years now and you can count the problems I came up against this substance on the fingers of one hand. But probably the major safety is in the reabsorption: even if a problem occurs, the substance will be reabsorbed over the time, and in most cases also the problem! It also has to be underlined that the syringes are rigorously “disposable” and they cannot be used for more than one patient. There are many types of hyaluronic acid and different producer brands: a less concentrated and one more concentrated. Beside, there are some biphasic and monophasic hyaluronic acid. Among the most important product we have: Restilane, Juvederm, XHa3, Regenial Idea, just to list some. They are used according to the depressions that need to be treated: more the wrinkles are thin, more the acid will be less concentrated. More the depressions are deep, more the acid will be concentrated. The results are really good and immediate. The collateral effects are rather scarce: · Swelling can occur and it is always due to the recall of water. As a rule it goes away in 24 hours and it interests more or less the 5% of the cases · Haematomas due to puncture of small capillaries and venulae. They do not last long, just few days. · Local erythema as soon as the treatment is over. They last few hours. · Reactions of intolerance: referred from the literature. They go away after few days and in rare cases after few weeks. In this case, the only certainty is that the substance will be reabsorbed after long time. · Asymmetries and swellings due to exaggerated corrections: if a rigorous technique is used, they will not occur. Up till now it remains the most used substance in the correction of wrinkles in Europe.