Fillers, also called dermal fillers, are gel-like substances injected beneath the skin to restore volume, smooth wrinkles, and enhance facial contours. They work by physically plumping the tissue at the injection site, and most types are temporary, lasting anywhere from 6 months to over 2 years depending on the material used. Fillers are one of the most common non-surgical cosmetic procedures, and understanding what goes into them can help you make sense of the options available.
What Fillers Are Made Of
Most fillers on the market today use one of three main materials, all of which are absorbable, meaning your body gradually breaks them down over time.
Hyaluronic acid (HA) is the most widely used filler material. It’s a sugar molecule that already exists naturally in your skin and cartilage. In filler form, it’s processed into a gel that can attract and hold up to 1,000 times its weight in water. When injected, that water-binding ability is what creates the plumping effect. HA fillers are chemically modified (crosslinked) so they hold their shape longer than the hyaluronic acid your body produces on its own. Common brand names include Juvederm, Restylane, and Belotero.
Calcium hydroxylapatite (CaHA) is a mineral found naturally in human teeth and bones. In filler form, tiny particles of it are suspended in a smooth gel and injected under the skin. CaHA fillers tend to be thicker than HA fillers and are often used for deeper wrinkles or adding volume to the back of the hands. The brand Radiesse is the most recognized CaHA filler.
Poly-L-lactic acid (PLLA) is a synthetic, biodegradable material also used in dissolvable stitches and surgical screws. Unlike HA and CaHA fillers, PLLA doesn’t just fill space. It triggers your body to produce new collagen at the injection site by stimulating certain immune cells that, in turn, signal your skin’s collagen-producing cells to ramp up output. Results build gradually over weeks rather than appearing immediately. Sculptra is the best-known PLLA filler.
How Fillers Work in Your Skin
Traditional fillers like HA and CaHA work primarily through direct volume replacement. The injected gel sits beneath the skin’s surface and physically pushes tissue outward, smoothing lines and restoring fullness that fades with age. HA fillers have an added benefit: the water they attract into the surrounding tissue creates a hydrating effect that improves skin softness and elasticity in the treated area.
There’s also a secondary effect. When HA gel is injected into the deeper layers of skin, it compresses the surrounding fibroblasts, the cells responsible for making collagen. That mechanical pressure stimulates them to produce new collagen over time, so the benefits extend slightly beyond the filler material itself.
PLLA fillers work differently. Rather than adding immediate volume, they act as biostimulators. The material triggers a controlled foreign body reaction led by immune cells called macrophages, which release signaling molecules that push fibroblasts to build new collagen. This is why PLLA results appear gradually over several weeks and can persist even after the filler material has fully dissolved. PLLA is typically administered in a series of injection sessions spaced over several months.
How Long Results Last
Longevity varies significantly by filler type. HA fillers typically last 6 to 18 months, depending on the specific product, the treatment area, and your individual metabolism. Areas with more movement, like the lips, tend to break down filler faster than areas like the cheeks.
CaHA fillers generally last around 12 to 18 months. PLLA fillers can produce results lasting more than 2 years, partly because the collagen your body builds in response to the material remains even after the PLLA itself is absorbed.
Fillers vs. Botox
People often confuse fillers with Botox, but they do fundamentally different things. Fillers add volume beneath the skin to fill in lines, plump features, and restore lost fullness. They treat static wrinkles, the kind you can see even when your face is completely relaxed.
Botox is a nerve-blocking agent that temporarily prevents muscles from contracting. It targets dynamic wrinkles, the lines that appear when you squint, frown, or raise your eyebrows. Botox is injected into the muscle itself, while fillers are placed in the space above or below muscles. The two are sometimes used together in different areas of the face, but they address different problems through completely different mechanisms.
What the Procedure Feels Like
A filler appointment is relatively quick. The provider marks strategic injection points on your face, then cleans the area with an antibacterial solution. To manage discomfort, they may apply a numbing cream, use a cold instrument to chill the skin, or inject a small amount of local anesthetic. Many filler products also contain a built-in numbing agent.
The injections themselves take only a few moments per site. After each injection, the provider massages the area and evaluates the result before deciding whether more filler is needed. The entire session can take as little as 15 minutes or up to an hour if multiple areas are being treated. Afterward, the area may feel tender for a day or two, but most people don’t need pain medication. Some swelling and bruising at the injection sites is normal and usually resolves within a week.
One Key Advantage of HA Fillers
A major reason HA fillers dominate the market is that they’re reversible. If you’re unhappy with your results, or if a complication arises, a provider can inject an enzyme called hyaluronidase that breaks down the hyaluronic acid gel. This enzyme targets only the filler material, not the hyaluronic acid your body produces naturally. Some results are visible immediately after the dissolving injection, but full breakdown takes up to two weeks. If you want new filler placed afterward, you’ll need to wait at least 14 days. CaHA and PLLA fillers cannot be dissolved this way, so their results must be waited out.
Risks and Side Effects
The most common side effects are mild and short-lived: redness, swelling, bruising, and tenderness at injection sites. These typically resolve on their own within a few days.
Serious complications are rare but worth knowing about. The most concerning is vascular occlusion, which happens when filler is accidentally injected into or compresses a blood vessel, blocking blood flow. This can lead to skin tissue damage, and in extremely rare cases involving vessels near the eyes, vision problems. Research calculating the incidence across a large treatment population found the risk of a vascular event is roughly 1 in 6,600 treatments, or about 0.015%. The risk is significantly lower when the procedure is performed by an experienced, properly trained provider who understands facial anatomy.
Other uncommon complications include infection, allergic reaction, and the formation of small lumps or nodules under the skin. CaHA fillers will show up on X-rays, which is worth mentioning to your radiologist if you have imaging done after treatment.
Cost
Fillers are priced per syringe, and most people need one to several syringes depending on the treatment area. The average cost of an HA filler syringe is $715, according to the American Society of Plastic Surgeons. Non-HA fillers like CaHA and PLLA average $901 per syringe. Lip augmentation with fillers averages $743. These figures vary based on your geographic location, the provider’s experience, and the specific product used. Health insurance does not cover fillers since they’re considered elective, but many practices offer financing plans.