Most dermal fillers are made from hyaluronic acid, a sugar molecule your body naturally produces in skin, joints, and eyes. But hyaluronic acid is just one category. Fillers also come in calcium-based, polymer-based, and permanent synthetic formulations, each with a distinct set of ingredients designed to add volume, smooth wrinkles, or stimulate your body’s own collagen production.
Hyaluronic Acid Fillers
Hyaluronic acid (HA) fillers are the most widely used type. Brands like Juvéderm, Restylane, Belotero, and Teosyal all belong to this category. The active ingredient is a gel made from hyaluronic acid, typically at concentrations between 12 and 26 mg per milliliter, depending on the product and its intended use. Thinner formulations with lower concentrations (around 12 to 15 mg/mL) are designed for delicate areas like lips or under-eye hollows, while denser versions (20 to 26 mg/mL) target deeper wrinkles and areas that need more structural support, like cheeks and jawlines.
The hyaluronic acid in these products isn’t harvested from humans or animals. It’s produced through bacterial fermentation in a lab, creating a biocompatible molecule identical to what your body already contains. This is one reason HA fillers carry a relatively low risk of allergic reactions.
Raw hyaluronic acid would dissolve in the body within days, so manufacturers chemically cross-link the molecules to make them last months or longer. The most common cross-linking agent is a chemical called BDDE (1,4-butanediol diglycidyl ether). BDDE creates bridges between HA chains, forming a stable gel network. During manufacturing, excess BDDE is washed out through dialysis. Regulatory standards limit residual BDDE to no more than 2 parts per million in the final product. Many HA fillers also contain lidocaine, a local anesthetic, at low concentrations to reduce pain during injection.
One practical advantage of HA fillers: they can be reversed. An enzyme called hyaluronidase breaks apart the chemical bonds holding hyaluronic acid together, dissolving the filler. Injecting 100 or more international units at each site produces a reliable effect. This reversibility is unique to HA fillers and is a major reason they remain the default choice for most cosmetic procedures.
Calcium Hydroxylapatite Fillers
Radiesse, the best-known product in this category, contains 30% synthetic calcium hydroxylapatite (CaHA) microspheres suspended in a 70% water-based gel carrier made from carboxymethylcellulose. The microspheres are tiny, between 25 and 45 micrometers in diameter, roughly the size of a fine grain of sand.
Calcium hydroxylapatite is the same mineral found naturally in human bones and teeth, which makes it highly biocompatible. After injection, the gel carrier provides immediate volume, then gradually dissolves over weeks. The calcium microspheres remain behind, acting as a scaffold that triggers your skin cells (fibroblasts) to produce new collagen around them. Over time, your body absorbs the microspheres entirely. This makes Radiesse both a filler and a collagen stimulator, providing volume immediately and then encouraging your skin to rebuild its own structural support. Unlike HA fillers, calcium-based fillers cannot be dissolved with an enzyme.
Poly-L-Lactic Acid Fillers
Sculptra is the primary product in this category. It arrives as a freeze-dried powder that gets mixed with sterile water before injection. Each vial contains 150 mg of poly-L-lactic acid (PLLA) microparticles, 90 mg of carboxymethylcellulose (a thickening agent that helps distribute the particles evenly), and 127.5 mg of mannitol (a sugar alcohol that prevents clumping during storage).
PLLA is a biodegradable synthetic polymer, the same family of materials used in dissolvable surgical sutures. It works differently from traditional fillers. Rather than adding volume directly, the microparticles trigger a controlled, low-level inflammatory response under the skin. Your body responds by gradually building new collagen around the particles over a period of weeks to months. The PLLA itself breaks down into lactic acid and is eventually metabolized. Results develop slowly, typically requiring two to three treatment sessions spaced several weeks apart, but they can last two years or more.
Permanent Fillers
The only FDA-approved permanent filler uses polymethylmethacrylate (PMMA) microspheres, the same type of plastic found in plexiglass and bone cement. These fillers are biphasic, meaning they contain two components: tiny PMMA beads suspended in a carrier solution of bovine (cow-derived) collagen or methylcellulose. Because the carrier contains animal-derived protein, skin testing for allergies is sometimes recommended before treatment.
After injection, the collagen carrier provides immediate volume and then gets absorbed by the body over several months. The PMMA microspheres remain permanently at the injection site, where they become encapsulated by your own collagen. The FDA has approved PMMA fillers only for nasolabial folds (the lines running from the nose to the corners of the mouth) and cheek acne scars. Their permanence is both the appeal and the risk: results last indefinitely, but complications are also permanent and more difficult to correct.
What Is Not in Approved Fillers
Injectable liquid silicone is not FDA-approved for any aesthetic use, including facial and body contouring. Despite this, illicit silicone injections still circulate through unregulated providers. Silicone injections can cause long-term pain, chronic infections, scarring, permanent disfigurement, and in severe cases, embolism (blockage of a blood vessel), stroke, or death. The FDA has been explicit: no injectable silicone product is approved for cosmetic enhancement.
All FDA-approved fillers are restricted to adults aged 22 and older. Temporary fillers are approved for moderate to severe facial wrinkles, skin folds, and volume augmentation of the lips, cheeks, chin, and backs of the hands. Permanent fillers have a much narrower set of approved uses.
How the Ingredients Differ by Purpose
The specific ingredients in a filler dictate how it behaves in your body and what it’s best suited for. Here’s a practical breakdown:
- Hyaluronic acid fillers: Provide immediate, reversible volume. Best for lips, under-eye hollows, fine lines, and areas where precision matters. Last 6 to 18 months depending on the product.
- Calcium hydroxylapatite (Radiesse): Provides immediate volume plus longer-term collagen stimulation. Best for deeper folds, cheeks, and jawline contouring. Lasts about 12 to 18 months. Not reversible.
- Poly-L-lactic acid (Sculptra): Provides gradual collagen rebuilding with minimal immediate volume. Best for overall facial volume loss and broad contouring. Results develop over months and last up to two years or more. Not reversible.
- PMMA (Bellafill): Provides permanent structural support. Limited approved uses. Best for deep nasolabial folds and certain acne scars. Not reversible.
Every approved filler also undergoes manufacturing controls to limit contaminants like bacterial endotoxins, residual cross-linking agents, and proteins. The concentrations of active ingredients, the size of microspheres, and the viscosity of the gel carrier all vary by product and are engineered for specific injection depths and facial zones. What feels like a simple syringe at your appointment is a precisely formulated medical device.