Why Fillers Are Temporary: How Is Hyaluronic Acid Broken Down?

In short: Hyaluronic acid (HA) fillers are a cross-linked, more durable form of a molecule that occurs naturally in the body, and over time they are broken down and absorbed by hyaluronidase enzymes and free radicals. How long the effect lasts depends on the treated area, the structure of the product, the amount injected and the person’s metabolism. If needed, HA fillers can be dissolved with the enzyme hyaluronidase; non-HA fillers behave differently.

One of the most common questions from people considering fillers is why the effect is temporary and “where the filler goes”. The answer lies in the natural turnover of hyaluronic acid in the body and in how filler products are made.

In this article we explain what hyaluronic acid is, the mechanisms by which it is broken down, the factors that influence how long it lasts, the role of hyaluronidase and how non-HA fillers differ. The information is general; which product and technique are suitable is decided at a physician’s examination.

What is hyaluronic acid?

Hyaluronic acid is a molecule made of sugar chains (a type of polysaccharide) that occurs naturally in the human body. It is found in high concentrations in the skin, joint fluid and the gel-like fluid inside the eye. Its most important property is its ability to bind many times its own weight in water, which gives tissues moisture, volume and elasticity.

The body’s own hyaluronic acid is constantly renewed: a large part of the natural HA in the skin is broken down and replaced within days. For this reason, pure, unmodified HA injected into the skin would disappear very quickly. To overcome this, the HA chains in filler products are linked together through a process called cross-linking, creating a gel that is more resistant to enzymes.

How is HA filler broken down in the body?

Cross-linked HA filler is eventually broken down by the body’s natural pathways as well. The process works mainly through two mechanisms:

• Enzymatic breakdown: Hyaluronidase enzymes naturally present in tissues cut HA chains into smaller fragments. Cross-links slow this process down but do not stop it.
• Free radicals (oxidative breakdown): Reactive oxygen species produced by metabolism, inflammation and external factors can also break HA chains.

Mechanical forces may also play a part: gel in an area that moves constantly is under more stress than gel in a more stable area. The small HA fragments are carried away through the lymphatic system, and most are processed in the liver and enter the body’s normal metabolism. In other words, the filler does not “build up somewhere”; over time it is broken down and cleared much like the body’s own HA.

Interestingly, according to some sources, HA continues to bind water as it degrades, so volume loss may feel slow and gradual for a while. The effect usually does not vanish overnight; it fades progressively. Some imaging studies have also reported that filler can still be detected in tissue for some time after the visible effect has diminished, which is why the status of earlier filler is considered before repeat treatments.

What affects how long it lasts?

There is no single duration that applies to everyone. The main factors are:

Factors that increase oxidative stress, such as prolonged sun exposure and smoking, are also thought to accelerate breakdown. On the effect of intense exercise, sources offer differing assessments. It is therefore more reliable to rely on your physician’s assessment of your own situation than on exact month counts shared online.

Hyaluronidase: can HA filler be dissolved if needed?

An important feature of HA fillers is that they can be dissolved, if needed, by injecting an enzyme called hyaluronidase. This enzyme speeds up the breakdown process the body naturally uses. Hyaluronidase may be considered in situations such as:

• Suspected entry of filler into a blood vessel or pressure on a vessel (vascular occlusion): this requires urgent treatment
• Unwanted excess, asymmetry or migration
• Nodules (small lumps) that can be felt or seen under the skin
• A bluish discolouration caused by very superficial placement (Tyndall effect)

Hyaluronidase treatment has its own risks; allergic reactions can occur rarely, and temporary swelling may develop. The enzyme can also temporarily affect the tissue’s own hyaluronic acid in the treated area. The physician therefore decides when and how much to use; rather than asking to have filler “dissolved” on your own initiative, it is important to have the situation assessed at an examination.

How do non-HA fillers differ?

Not all fillers contain hyaluronic acid, and non-HA products behave differently in the body. Fillers containing substances such as calcium hydroxylapatite or poly-L-lactic acid aim to stimulate collagen production in addition to providing volume (they are also referred to as biostimulators); the body breaks them down through different pathways and usually more slowly. Some products are designed to be permanent or semi-permanent.

What these products have in common is that they cannot be dissolved with hyaluronidase. If a problem arises, correction can be more difficult. For this reason, HA fillers are often preferred, particularly for first-time treatments and delicate areas, because of their reversibility. Which product is appropriate is determined by a physician’s assessment of the area and the person’s expectations.

Frequently Asked Questions

Does hyaluronic acid filler accumulate in the body?

According to generally accepted knowledge, HA filler does not permanently accumulate in the body. Over time it is broken into small fragments by hyaluronidase enzymes and free radicals in the tissues, carried away by the lymphatic system and mostly processed in the liver. Filler may, however, remain in the tissue for a while after the visible effect has faded, which is taken into account when planning repeat treatments.

Why does lip filler wear off faster than cheek filler?

The lips move constantly with speech, eating and facial expressions, and this mobility increases the mechanical load on the gel. Softer, more flexible products are also usually chosen for the lips, whereas denser products can be used in more stable areas such as the cheeks and chin. For these reasons, lip filler usually lasts shorter, although duration still varies from person to person.

Can filler be completely dissolved with hyaluronidase?

Hyaluronidase can largely dissolve HA fillers by breaking them down; the amount and number of sessions needed depend on the product’s structure and the volume present. The enzyme only works on fillers containing hyaluronic acid and has no effect on calcium hydroxylapatite, poly-L-lactic acid or permanent fillers. The physician decides on its use after asking about any allergy history.

Does exercise make filler break down faster?

Sources offer differing assessments on this. Although a high metabolic rate and intense exercise have been suggested to speed up breakdown somewhat, the size of the effect is unclear. Avoiding intense exercise in the first days after treatment is generally advised to limit swelling and bruising. You can ask your physician how long this applies in your case.

When the filler wears off, will my face look saggier than before?

According to generally accepted knowledge, HA filler does not leave the tissue worse than before treatment when it is absorbed; the effect fades gradually and the face reflects the natural ageing that has continued in the meantime. Excessive and very frequent treatments, however, may stretch the tissue, so the amount and intervals should be planned with the physician.

For more information on the scope of filler treatments, you can visit the Fillers and Mesotherapy page, and use the Contact page to arrange an examination in Kayseri.

This article is for informational purposes only; a physician’s examination is required for diagnosis and treatment.