A dermal filler is a gel-like substance injected beneath the skin to restore lost volume, smooth wrinkles, or enhance facial contours. Most fillers are made from hyaluronic acid, a sugar naturally present in your skin, cartilage, and other tissues. When placed under the skin, the gel binds to water molecules and swells, creating a plumping effect that fills in lines and adds fullness to areas like the cheeks, lips, and jawline.
How Dermal Fillers Work
As you age, your skin loses fat, collagen, and moisture. This creates hollows under the eyes, flattened cheeks, deeper folds around the mouth, and thinner lips. Fillers work by physically occupying that lost space. A practitioner injects a small amount of gel at specific depths beneath the skin, and the material pushes tissue outward to restore a smoother, fuller appearance.
Hyaluronic acid fillers work partly through chemistry. The molecule has hydrophilic (water-attracting) groups that form hydrogen bonds with surrounding water, causing the gel to swell inside the tissue. This is what gives the treated area its volume and soft feel. Other filler types take a different approach: some stimulate your body to produce its own collagen over time rather than simply filling space with gel.
Types of Filler Materials
The FDA has approved four main categories of filler substances, each with different properties and uses:
- Hyaluronic acid (HA) is the most common type. It’s a natural sugar already present in your body, which makes allergic reactions rare. HA fillers are soft, versatile, and reversible. They typically last 6 to 18 months depending on the product and where it’s placed.
- Calcium hydroxylapatite is a mineral found naturally in teeth and bones. It’s thicker than HA, making it better suited for deeper lines and areas like the cheeks. It also stimulates some collagen production and can last longer than HA.
- Poly-L-lactic acid (PLLA) is a biodegradable synthetic polymer that works as a collagen stimulator rather than a traditional filler. Results build gradually over several treatment sessions and can last over two years.
- PMMA microspheres are tiny, non-biodegradable beads suspended in a gel. This is the only permanent filler option among FDA-approved products, which makes it the least forgiving if something goes wrong.
Fillers vs. Botox
People often confuse fillers with Botox, but they solve different problems. Botox is a neurotoxin that temporarily paralyzes small facial muscles. It’s designed for dynamic wrinkles, the lines that form when you smile, squint, or frown (think crow’s feet and forehead lines). Fillers, by contrast, treat static wrinkles: the lines visible even when your face is completely relaxed, like nasolabial folds or marionette lines around the mouth.
Put simply, Botox relaxes muscles to prevent wrinkles from forming. Fillers add volume to fill in wrinkles that are already there. Some people get both in the same appointment, targeting different areas of the face with each.
How Long Results Last
Most hyaluronic acid fillers last between 6 and 18 months. The range is wide because longevity depends on the specific product, where it’s injected, and your individual metabolism. Filler placed in areas with a lot of movement (like the lips) tends to break down faster than filler in relatively still areas (like the cheeks).
Collagen-stimulating fillers like PLLA and calcium hydroxylapatite generally last longer, often over two years. Their results also look different over time. Instead of a single injection producing immediate fullness, these fillers encourage your body to build new collagen gradually, so the effect develops over weeks or months and fades more slowly.
People with faster metabolisms tend to break down filler more quickly. Physical activity level, sun exposure, and overall health can also influence how long your results hold.
One Key Advantage of HA Fillers: Reversibility
Hyaluronic acid fillers have a unique safety advantage. If you dislike your results or develop a complication, an enzyme called hyaluronidase can dissolve the filler. This enzyme breaks the chemical bonds holding the HA gel together, causing it to break down and be absorbed by your body.
After a dissolving treatment, practitioners typically assess results at 48 hours and can repeat the process if needed. Post-treatment swelling can take longer to fully resolve, so waiting at least two weeks before placing new filler ensures a more predictable outcome. Non-HA fillers cannot be dissolved this way, which is one reason HA remains the most popular choice, especially for first-time patients.
Common Side Effects
Most side effects are mild and short-lived. Bruising, redness, swelling, tenderness, and itching at the injection site are all normal. These typically peak within the first 24 hours and resolve within a few days to a week.
Less common complications include small raised bumps under the skin (called nodules or granulomas), infection, allergic reactions, and prolonged inflammation that can flare after illnesses, vaccinations, or dental procedures.
The most serious risk is accidental injection into a blood vessel. Filler that enters a blood vessel can block blood flow, potentially causing tissue death, vision loss, or stroke. This is rare, but it’s the primary reason choosing a qualified, experienced injector matters more than the brand of filler or the price of the treatment.
What Recovery Looks Like
There’s essentially no downtime. Most people return to work or normal activities the same day. That said, the first 24 hours are when swelling and redness are most noticeable, so it’s worth planning around social events.
For the first few days, you’ll want to avoid touching or massaging the treated area, skip strenuous exercise, and stay away from alcohol and excessive salt, all of which can worsen swelling. Sleeping with your head slightly elevated on an extra pillow helps limit fluid buildup. Saunas, hot tubs, and prolonged sun exposure should be avoided for at least two to three days.
You’ll see a visible improvement within the first week, but optimal results typically appear around two to three weeks after treatment, once swelling has fully settled and the filler has integrated with your tissue. At that point, you can resume aggressive skincare products like retinoids and exfoliating acids, though it’s best to keep them away from injection sites for that full first week.
Who May Not Be a Good Candidate
Fillers aren’t appropriate for everyone. People with active skin infections near the treatment area, known allergies to filler ingredients, or certain autoimmune conditions may face higher risks. Pregnant or breastfeeding individuals are generally advised to wait, as filler safety hasn’t been studied in those populations. A history of severe scarring or keloid formation can also complicate results. If you have any of these concerns, they’re worth discussing with your provider before booking a treatment.