Learning Center: INJECTABLES

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TYPES OF INJECTABLES (NEUROMODULATORS VS. FILLERS)

In brief

Facial injectables fall into two broad groups. Neuromodulators (botulinum toxin products such as Botox, Dysport, Xeomin, Jeuveau and Daxxify) relax specific muscles and soften the lines those muscles create; the effect usually lasts about three to four months. Fillers restore lost volume or support. Hyaluronic acid fillers are the most common, typically last from about six months to two years depending on the product and the area, and can be dissolved with an enzyme. Autologous fat transfer uses a person's own fat as a filler and can last much longer, but it requires a minor surgical harvest and a variable portion of the fat does not survive. Serious complications are rare. The most important is the accidental injection of filler or fat into a blood vessel, which can injure skin and, very rarely, cause blindness.

Two different problems, two different tools

Facial aging is a combination of several processes: skin thinning and loss of elasticity, repeated muscle movement that etches lines into the skin, and loss and descent of the deep fat compartments and bone that support the face (see aging and aesthetics). Injectables address the last two.

Dynamic lines appear with expression: the vertical "11s" between the brows when frowning (glabellar lines), horizontal forehead lines when raising the brows, and crow's feet at the outer corners of the eyes when smiling. These are produced by muscle contraction, and they respond best to a neuromodulator, which weakens that contraction [1].
Static lines and volume loss are present at rest: deepening folds from the nose to the mouth (nasolabial folds), flattening of the cheeks, hollowing under the eyes, thinning lips, and lines around the mouth. These reflect loss of tissue rather than muscle activity, and they respond to replacement of volume with a filler or with fat [2, 3].

Many people have both, and the two treatments are often combined. Injectables do not tighten loose skin or lift a sagging jowl or neck in the way that surgery does; when skin laxity is the main problem, a facelift, necklift or brow lift is usually more effective. Surface texture, fine crinkling and pigment respond better to a good skin regimen and to skin resurfacing.

An overview of how injectables fit with other options is on the aesthetic treatments page, and practical preparation tips are on making the most of your aesthetic visit.

NEUROMODULATORS

How they work

Botulinum toxin type A blocks the release of acetylcholine, the chemical signal that a nerve uses to tell a muscle to contract. When small, precisely placed doses are injected into a facial muscle, that muscle relaxes partially, and the skin over it creases less. The nerve gradually sprouts new connections, so the effect wears off over several months and the muscle returns to normal [4]. More detail on the products used in the practice is on the cosmetic neurotoxins page; botulinum toxin also has medical uses, described on the neurotoxins page.

The products

Several botulinum toxin type A products are available in the United States: onabotulinumtoxinA (Botox Cosmetic), abobotulinumtoxinA (Dysport), incobotulinumtoxinA (Xeomin), prabotulinumtoxinA (Jeuveau) and daxibotulinumtoxinA (Daxxify). Each is measured in its own units, and units are not interchangeable between products, so a "20-unit" dose of one brand is not equivalent to 20 units of another [1, 5]. In a Cochrane review of 65 randomized trials, abobotulinumtoxinA 50 units and onabotulinumtoxinA 20 units had equivalent success rates for frown lines, as did incobotulinumtoxinA and onabotulinumtoxinA at 24 units each [1].

Areas treated and how well it works

Botulinum toxin is approved by the U.S. Food and Drug Administration (FDA) for frown lines (glabellar lines), crow's feet (lateral canthal lines) and forehead lines, and for vertical neck bands caused by the platysma muscle [4, 6, 7]. Other uses, such as softening a downturned mouth corner, a "gummy" smile, or a bulky jaw muscle (masseter), are common but are off-label.

Frown lines. In the Cochrane review, people treated with onabotulinumtoxinA 20 units were about 17 to 19 times more likely than those given placebo to have a successful result at four weeks (moderate-certainty evidence), with similar results for the other products [1].
Crow's feet. In a phase 3 trial of 917 adults, about 55% of treated patients (investigator assessment) reached "none" or "mild" crow's feet at maximum smile at day 30, compared with 3% given placebo [8].
Forehead lines. Forehead lines are treated together with the frown lines, because relaxing the forehead muscle alone can let the frown muscles pull the brows down. In two pooled phase 3 trials (865 subjects), satisfaction improved significantly and was sustained [9].
Neck bands. In two phase 3 trials of onabotulinumtoxinA for prominent platysma bands, 64% of treated participants were satisfied with treatment at day 14, compared with about 12% given placebo [7]. Botulinum toxin softens bands but does not correct loose neck skin.

Onset and duration

Results begin within a few days. In the abobotulinumtoxinA phase 3 program, effect appeared as early as 24 hours, with a median onset of three days [10]. For the conventional products, the effect typically wears off at about three to four months [5]. In the abobotulinumtoxinA trials, the median duration of response was 85 to 109 days depending on the dosing scheme [10]. DaxibotulinumtoxinA, which is formulated with a stabilizing peptide rather than human albumin, maintained "none or mild" frown lines for a median of 24 weeks in two phase 3 trials of 609 participants [11, 5]. Efficacy was maintained over repeated cycles in long-term extension studies [10].

Side effects and safety

Common and minor: brief stinging, small bruises, and headache. In the daxibotulinumtoxinA trials, treatment-related headache occurred in 6.4% versus 2.0% with placebo [11].
Eyelid or brow droop (ptosis): the main "major" adverse event across all products in the Cochrane review [1]. In the 2002 pivotal frown-line trial it occurred in 5.4% of treated patients and was mostly mild [12]. It is temporary, generally resolving over several weeks. A heavy brow can also result if the forehead is over-treated; when excess eyelid skin is the real problem, blepharoplasty may be the better treatment (see also aging eyes).
Less common: double vision, dry eye, an asymmetric smile, or eyelid sensory symptoms, all temporary [1, 13].
Loss of response: the body can form neutralizing antibodies to the toxin, but in cosmetic use this is uncommon. An overview of systematic reviews (more than 17,000 patients) found nil to insignificant antibody rates in aesthetic use [14].

Botulinum toxin is generally avoided during pregnancy and breastfeeding and in people with neuromuscular disorders such as myasthenia gravis.

FILLERS

Hyaluronic acid fillers

Hyaluronic acid (HA) is a sugar molecule found naturally in skin, where it holds water. Filler products chemically cross-link HA into a gel so that it resists breakdown and stays in place. Brands include the Juvéderm, Restylane, RHA and Belotero families, each with gels of different firmness. Softer gels suit the lips and fine lines; firmer gels are placed deep to restore the cheek, chin or jawline. Manufacturing technology differs between product lines, so HA fillers are not interchangeable [2, 15].

Common sites are the cheeks and midface (restoring flattened cheeks also softens the nasolabial fold and the hollow beneath the eye; see cheek treatments), the lips and the area around the mouth (see lip treatments), the chin, jawline and temples, some depressed scars, and the tear trough between the lower eyelid and cheek. The tear trough is delicate: delayed swelling, lumps, migration and discoloration can occur, sometimes many months later [16].

How long HA fillers last

Results are immediate. Duration depends on the product, how much the area moves, and individual metabolism. A 2026 systematic review of 24 studies (1,410 patients) with at least 12 months of follow-up found, on 3D volume measurement, that 60% to 86% of the filler effect persisted at 12 months and 50% to 86% at 24 months [2]. In the pivotal trial of a volumizing cheek filler (Juvéderm Voluma), 86% of treated patients improved by at least one grade at six months, and nearly half maintained their correction at two years [3]. In the lips, which move constantly, results have been shown to persist through 48 weeks in a randomized trial [17]. As a general guide, lip and fine-line products tend to be refreshed in 6 to 12 months and deep cheek products in 12 to 24 months.

Reversibility: hyaluronidase

A key safety advantage of HA fillers is that they can be dissolved with an injected enzyme, hyaluronidase. This allows correction of an unwanted result or a lump and, most importantly, treatment of a blocked blood vessel. Products differ in how easily they dissolve: in laboratory testing of 16 fillers, manufacturing technology was the main factor, with the Vycross family (for example, Voluma and Volbella) the most resistant [15]. In a randomized study in volunteers, Restylane responded to very low enzyme doses, whereas Voluma needed more than 20 units per 0.2 mL of filler [18]. For routine reversal, modest doses are usually effective; another randomized study found no difference between 20 and 40 units [19].

Biostimulatory fillers: CaHA and PLLA

Calcium hydroxylapatite (CaHA, Radiesse) consists of tiny mineral spheres in a gel carrier. It gives immediate volume, and the spheres then stimulate the skin to produce new collagen. Poly-L-lactic acid (PLLA, Sculptra) works almost entirely through collagen stimulation: it is given as a series of sessions several weeks apart, and the result develops gradually over months. A 2026 systematic review found that PLLA effects lasted up to about 25 months and CaHA effects 12 to 18 months, with improvements in skin elasticity, wrinkles and facial volume [20]. In a meta-analysis of 25 studies of biostimulators, satisfaction was 91%; pain at injection was nearly universal, bruising occurred in about 27%, and nodules (small firm lumps) in about 5% [21]. Unlike HA, they cannot be dissolved [22].

Common side effects

Swelling, redness and bruising are expected and usually settle within one to two weeks. In an analysis of 2,813 filler adverse events reported to the FDA, the most frequent were swelling (60%), nodules (34%) and pain (23%), and the cheeks, lips and nasolabial folds were the sites most often involved [23]. Delayed lumps or swelling, appearing weeks to months later, may be inflammatory or infectious; in the systematic review supporting the American Society for Dermatologic Surgery (ASDS) guideline, treatment with antibiotics, corticosteroids, 5-fluorouracil and hyaluronidase was associated with response in 75% to 80% of cases [24, 25].

Vascular occlusion and skin injury

The most important filler complication is injection into, or compression of, an artery. This blocks blood flow to the skin that the artery supplies. Warning signs are disproportionate pain, blanching of the skin, and then dusky, mottled discoloration; without treatment, the skin may break down and scar. The ASDS review estimated skin necrosis at roughly 5 per 1,000 patients, with improvement in up to 77% of cases when treated [24]. For HA filler, the treatment is prompt, repeated, high-dose hyaluronidase flooded into the affected area until circulation returns; one widely used protocol reported no skin loss when it was started within two days, and its author stresses that no area of the face is entirely free of this risk [26].

Blindness

Very rarely, filler travels backward through facial arteries into the artery that supplies the eye, causing sudden and usually permanent loss of vision, sometimes with stroke. The ASDS review estimated the risk at about 1 to 2 per 1,000,000 patients [24]. A review of all published cases from 2018 to 2023 identified 365 new cases worldwide. The highest-risk sites were the nose (41%), forehead (28%) and glabella between the brows (19%), and HA was the filler in 80%. Of the cases that reported outcomes, only 6% recovered vision completely, 26% improved partially and 68% did not recover; no treatment was significantly associated with recovery [27]. Earlier reviews reached similar conclusions [28, 29].

Because treatment after the fact is so limited, prevention matters most. International consensus recommendations emphasize a thorough knowledge of facial vascular anatomy, informed consent that includes this risk, slow low-pressure injection of small volumes, use of blunt cannulas in selected areas, caution in the nose, forehead and glabella, and having hyaluronidase and an emergency plan immediately available [30, 25].

AUTOLOGOUS FAT TRANSFER

What it is

Autologous fat transfer (also called fat grafting or lipofilling) uses a person's own fat as a filler. Fat is harvested with a thin suction cannula, usually from the abdomen or thighs, processed to remove fluid and oil, and re-injected in tiny parcels into the cheeks, temples, lower-eyelid hollows, lips or jawline. It is often done together with a facelift or eyelid surgery, since loss of facial volume and loose skin usually coexist.

How much of the fat survives

Transferred fat must establish a new blood supply to survive, and not all of it does. A meta-analysis of 27 studies (1,011 patients) found that the pooled volume retained after facial fat grafting was 47%, with individual studies ranging from 26% to 83%; the way volume was measured strongly influenced the reported result, and the authors concluded that retention in any one patient is currently unpredictable [31]. A second meta-analysis estimated 12-month retention at 64% for mixed facial deformities but 43% for acquired atrophy (volume loss), the category that includes age-related change [32]. A second session is sometimes needed. Fat that survives the first few months is generally long-lasting.

Several refinements aim to improve survival. A systematic review of processing techniques found that washing and filtration of the fat produced better long-term outcomes than centrifugation or simple settling, and that enrichment with the fat's own stem and stromal cells gave higher facial volume retention [33]. In a small multicenter randomized trial, enrichment with the stromal vascular fraction increased fat survival on MRI at 24 weeks to about 71%, versus about 62% without enrichment [34].

Recovery and complications

Swelling after facial fat grafting is more pronounced and lasts longer than after filler, often two to three weeks, with bruising at both the harvest and injection sites. In the American Society of Plastic Surgeons' prospective registry of 7,052 fat grafting procedures, the complication rate for the face was 1.94%; the most common problems were a palpable lump (0.54%) and infection (0.54%) [35]. A meta-analysis of 31 studies reported surgeon and patient satisfaction of 97% and 95%, with a pooled complication rate of 3.4% [32]. Not every review is as reassuring: a systematic review found reported complication rates ranging from 1.5% to 81.4%, reflecting inconsistent reporting; irregularities, prolonged swelling, graft overgrowth, fat necrosis and acne flares were most common, and lumps or asymmetry often required a touch-up [36].

The most serious risk is the same as with fillers: injection into an artery. Fat cannot be dissolved, and fat emboli to the eye or brain can cause permanent blindness or stroke [36, 13]. In the 2015 world literature review of 98 cases of vision loss after facial injection, autologous fat was the material involved in 48% of cases, more than any filler [28]. The precautions described above for fillers apply equally to fat.

Summary

Neuromodulators relax muscles to soften expression lines, work within days, last about three to four months, and are among the best-studied treatments in aesthetic medicine; their main risk is a temporary droop of the eyelid or brow. Fillers replace lost volume. Hyaluronic acid fillers last roughly 6 to 24 months and can be dissolved, biostimulators last roughly one to two years but cannot be dissolved, and fat transfer can be permanent but requires a surgical harvest and survives unpredictably. Every filler and fat injection carries a small risk of blocking a blood vessel, which can injure skin or, very rarely, cause blindness.

Last reviewed: October 4, 2026

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