Hyaluronic acid injections are used to improve the appearance of the skin, as a dermal filler to smooth wrinkles, and to increase volume in some specific areas of the face, such as the lips and cheeks. Hyaluronic acid treatments are growing rapidly in the world of aesthetic medicine because they are non-invasive. Being a natural component of the skin, it is assimilated and reabsorbed by the body through a degradation process that can last for months. In general, there are many doubts about the reabsorption process of hyaluronic acid and there are even different publications that question this fact, something totally discarded by specialists in aesthetic medicine.
How is hyaluronic acid reabsorbed?
Immediately after injection, the hyaluronic acid disperses in the treated area and integrates into the surrounding tissues. Due to its ability to attract and retain water, it provides volume and hydration, improving the appearance of the skin and smoothing wrinkles or folds. The effects of injected hyaluronic acid are not permanent. Depending on the type of product used, the cross-linking, the area of injection and the patient’s individual metabolism, the effects can last from several months to a year. The duration can also be influenced by factors such as the amount of hyaluronic acid injected, the injection technique and the patient’s lifestyle. It may happen that the absorption of hyaluronic acid is prolonged beyond normal. According to the Spanish Society of Aesthetic Medicine (SEME), this can occur, especially if the frequency of injections is not respected. That is, if injections are accumulated without the product of the previous ones having dissolved completely. Over time, what is called enzymatic breakdown begins. The body begins to break down the hyaluronic acid through the action of an enzyme called hyaluronidase, which is naturally present in the body and helps to break down the hyaluronic acid into its basic components, which are then eliminated or reused by the body. Finally, the degraded components of hyaluronic acid, mainly glucosamine and glucuronic acid, are absorbed by the cells and eliminated through normal metabolic processes. They can be reused by the body for other biological functions.
How does hyaluronidase behave?
The human body produces hyaluronidase naturally, and this enzyme is found in various tissues and body fluids. The enzyme breaks the glycosidic bonds between disaccharide units, facilitating the reduction of hyaluronic acid viscosity and allowing its absorption and elimination by the body. It catalyzes the hydrolysis of hyaluronic acid, breaking it down into its basic components, which are smaller disaccharides such as glucuronic acid and N-acetylglucosamine. Occasionally, hyaluronidase can also be administered externally as an injection to dissolve injected hyaluronic acid in aesthetic treatments.
Can heat accelerate the dissolution of hyaluronan?
Heat can increase the activity of the enzyme hyaluronidase, which is responsible for breaking down hyaluronic acid in the body. At higher temperatures, enzymatic reactions tend to occur more rapidly, which can accelerate the degradation of hyaluronic acid. Now, it has to be a prolonged exposure. Nothing is going to happen if you sunbathe for a whole day or have a radiofrequency treatment months after the injection. In these cases, the increase in body temperature is temporary and is usually not enough to noticeably accelerate hyaluronidase activity or blood flow in a way that affects the duration of the hyaluronic acid. Prolonged and intense exposure to heat can increase the local temperature of the treated area, increase enzyme activity and blood flow, thereby accelerating the dissolution of hyaluronic acid and reducing the duration of its effects.
What is hyaluronic acid cross-linking?
Cross-linking is a chemical process that modifies the structure of hyaluronic acid to increase its stability and durability. This process is essential for the creation of dermal filler products that are more resistant to enzymatic degradation and therefore provide longer lasting effects when used in aesthetic treatments.
- Cross-linking allows the effects of dermal fillers to last longer, often between 6 months and 2 years, depending on the degree of cross-linking and the specific product.
- It also affects the consistency and elasticity of the final product. More cross-linked products tend to be firmer and suitable for volume and structure, while less cross-linked products are softer and more flexible, suitable for smoothing fine wrinkles.
- Although crosslinking modifies the hyaluronic acid, the resulting products remain biocompatible and safe for human use.