Written and medically reviewed by Dr. Kamen Ng. Last reviewed 2026-10-08. 18 min
By Dr. Kamen Ng · Head of Aesthetic Medicine, AOKLINIK
Every injector who works long enough will see complications. Anyone claiming otherwise has either not worked much or is not counting honestly.
What separates competent practice from the alternative is not an absence of problems. It is recognising them quickly, knowing the time window for each, and having what is needed in the building when the window is short.
This article is more detailed than most patient-facing writing on the subject, deliberately. I have been asked these questions enough times, usually by people who have had something go wrong elsewhere and were given no explanation, that the information seems worth setting out properly.
I have not included drug doses. Those are prescribing decisions and they belong in a clinical setting, not in an article. Everything else is here.
If you are currently experiencing symptoms, skip to the section on warning signs near the end, or go to an emergency department now if you have pain that is escalating, skin turning white or mottled, or any change in vision.
Part one: botulinum toxin
Toxin complications are, with one or two exceptions, temporary. That is genuinely reassuring and it is not the same as trivial, because temporary can mean three months of looking wrong.
Eyelid ptosis
The drooping upper lid. Uncommon, distressing, and almost always technique-related.
Mechanism. Toxin spreads through the orbital septum and reaches the levator palpebrae superioris, the muscle that holds the upper lid open. It usually follows injection placed too low or too medially near the corrugator, too close to the orbital rim, or a treatment where excessive volume or dilution has encouraged spread. Rubbing the area or lying down soon afterwards can contribute.
Timing. Typically appears between two and ten days after treatment, often peaking around two weeks. A lid that droops immediately after injection is swelling, not ptosis.
Duration. Usually three to six weeks, occasionally longer, resolving as the affected fibres recover.
Management. There is no reversal agent for botulinum toxin. What exists is a workaround that is genuinely useful: eye drops from the alpha-adrenergic agonist class stimulate Müller's muscle, a small smooth muscle that contributes to lid elevation and is not affected by the toxin. This typically lifts the lid by a millimetre or two, which is often enough to look normal. It is symptomatic rather than curative and it is used until the effect wears off. These drops are not suitable for everyone, including some people with glaucoma, which is one reason this is a prescription rather than something to source yourself.
Prevention. Respecting the distance from the orbital rim, injecting above a defined line, avoiding excessive dilution in that region, placing small accurate aliquots, and advising patients not to rub the area or lie flat for several hours.
Brow ptosis and the heavy forehead
A different problem that patients frequently describe in the same words, and the distinction matters because the management differs completely.
Mechanism. The frontalis is the only muscle that lifts the brow. Over-treating it, particularly in its lower fibres, removes that lift. The patients most at risk are those who have been unconsciously using frontalis to compensate for descending brows or excess upper lid skin. They were holding their brows up all day, and treatment removed the mechanism.
Presentation. Not a drooping lid but a sensation of heaviness, eyes that feel harder to open, and a tired appearance. It frequently shows most at the end of the day.
Duration. Six to twelve weeks typically, since it resolves only as frontalis function returns.
Management. There is no reversal. Partial rebalancing is sometimes possible by treating the muscles that pull the brow down, the corrugator, procerus and the lateral orbicularis, which allows whatever frontalis function remains to work less opposed. It helps; it does not fix.
Prevention is where the real work is. Assessing the brow at rest, asking the patient to relax the forehead completely to see where the brow actually sits, and identifying frontalis-dependent patients before treating them. In that group, conservative forehead dosing or none at all is the right answer, and saying so is better practice than treating and hoping.
Lateral brow peaking
The arched or quizzical brow, sometimes called a Spock or Mephisto brow.
Mechanism. The central frontalis is treated while the lateral fibres are not, so the untreated lateral portion pulls unopposed.
Management. The most satisfying correction in aesthetic medicine. A very small dose into the lateral frontalis above the peak, and it settles within days. It is a reason to attend a two-week review rather than a reason for alarm.
Asymmetry
Common, and frequently pre-existing rather than created. Most faces are asymmetrical and most people have never examined their own closely. Treatment can unmask what was already there.
Management. Photography before treatment, assessment at a two-week review, and a small top-up to the stronger side. This is routine work and it is why a review should be part of the price rather than an extra.
The less common ones
Dry eye or incomplete lid closure from over-treating the orbicularis. Managed with lubricants and time.
Double vision, rare, from spread to an extraocular muscle, usually following injection too low in the crow's feet region. Needs ophthalmological assessment.
An altered smile, from toxin affecting the muscles that elevate or depress the lip. This occurs with perioral work and occasionally after masseter treatment where the product reaches nearby muscles of expression.
Paradoxical masseter bulging on chewing, where posterior fibres are treated and anterior fibres compensate. Managed by treating the remaining fibres.
Headache in the days afterwards, common and self-limiting.
Part two: filler, and the one true emergency
Vascular occlusion
This is the complication that organises everything else about how an injectable practice should be run.
Mechanism. Either product enters an artery directly, or it compresses one from outside. Either way, blood supply to the tissue downstream is interrupted. If the territory connects back towards the eye, product can travel retrograde and occlude the ophthalmic circulation.
The anatomy that matters. The highest-risk sites are the glabella, the nose including dorsum and alae, the nasolabial fold, the forehead, the temple and the infraorbital region. The nose deserves particular caution, because its supply has limited alternative routes and the risk is higher again in a nose that has had surgery.
How it presents, in sequence.
Immediately: pain that is disproportionate to the procedure, usually severe and increasing rather than settling, and blanching of the skin as the blood supply stops. Not every case is painful, which is why colour change matters as much as symptoms.
Within hours: a dusky, mottled, net-like discolouration across the affected territory, with delayed refilling when the skin is pressed.
Within days: pustules and blistering.
Later, if untreated: a dark eschar and tissue loss, which heals with scarring.
The ocular presentation is different and faster. Sudden severe eye pain, loss of vision, drooping, restricted eye movement, sometimes nausea and vomiting. This usually occurs at the moment of injection rather than later. Retinal tissue tolerates ischaemia for a very short period, which is why this is measured in minutes rather than hours.
Management of cutaneous occlusion. Stop injecting immediately. The treatment is hyaluronidase, given in high dose, flooding the whole affected vascular territory rather than the injection point, and repeated at intervals until colour and capillary refill return. This frequently means considerably more product than a clinic stocking a single vial would have available, which is why the question "do you keep hyaluronidase on the premises" should really be "how much".
Supportive measures include warmth and massage to encourage flow, and an antiplatelet agent where there is no contraindication. Topical vasodilator paste is described in some protocols and remains debated, with a reasonable argument that increasing flow could distribute embolic material further, so it is not universal practice.
Hyperbaric oxygen has been used as an adjunct in tissue ischaemia and compromised flaps, on the rationale of improving oxygen delivery to marginally perfused tissue. The evidence specifically in filler-induced vascular compromise is limited and largely at the level of case reports rather than trials. We have a hyperbaric facility and we have used it adjunctively, and I would describe it honestly as a supportive measure alongside hyaluronidase rather than as a substitute for it or as an established treatment.
Management of ocular involvement is immediate referral to ophthalmology. Retrobulbar hyaluronidase is described in the literature, the evidence for it is weak, and it requires someone trained to administer it. The genuinely important thing is speed of referral.
Prevention, which matters more than any protocol. Knowing the anatomy of the area being treated. Cannula rather than needle in appropriate planes. Slow injection under low pressure. Small aliquots rather than a bolus. Keeping the needle moving. And in the highest-risk zones, choosing a reversible product, because that choice is what makes any of the above possible.
Early nodules
Lumps appearing within days to a few weeks.
Mechanism. Usually technique. Product placed too superficially, too much in one place, in the wrong plane, or in tissue too mobile to hold it.
Management. Massage in the first instance for minor irregularity. For hyaluronic acid, small precise doses of hyaluronidase resolve this reliably, and the ability to do that is one of the strongest arguments for reversible product in a first-time patient.
Delayed-onset nodules
Appearing weeks, months or occasionally years later, and a quite different problem.
Mechanism. Inflammatory rather than mechanical, and often triggered by something unrelated: a viral illness, a dental infection, a vaccination, a procedure elsewhere. The product has been sitting quietly and the immune system changes its mind about it.
The important distinction is infection versus inflammation, because treating one as the other makes things worse. A low-grade bacterial biofilm on the implant presents similarly to an inflammatory nodule, and injecting steroid into an infected nodule is actively harmful.
Management therefore usually begins with antibiotic cover, with agents chosen for their activity against biofilm as much as for their antibacterial effect. Once infection is addressed, anti-inflammatory treatment including intralesional steroid may follow, sometimes with additional agents for resistant nodules. For hyaluronic acid, dissolving the product removes the antigen and is frequently the cleanest answer. Occasionally excision is required.
This is also why your history matters. A patient who develops a facial nodule three days after dental work, or during a flu, has given us the most useful piece of information available.
Nodules from biostimulators
A separate category because the main tool is unavailable.
Calcium hydroxyapatite and poly-L-lactic acid have no reversal agent. Nothing dissolves them. Management relies on massage, dilution, intralesional steroid, time and occasionally minor surgery. Most resolve. It takes considerably longer and more intervention than the equivalent hyaluronic acid problem.
I raise this because it belongs in the consent conversation before treatment, and in my experience it frequently is not.
The Tyndall effect
The bluish or greyish discolouration seen when hyaluronic acid sits too superficially under thin skin, most often beneath the eyes.
Mechanism. Light passing through a translucent gel scatters, and shorter blue wavelengths scatter more than longer red ones. The same physics makes the sky blue and makes the veins on your wrist look blue when the blood inside them is not.
It will not fade, because nothing is resolving. The gel is simply in the wrong layer.
Management. Hyaluronidase, in small precise amounts. One of the more straightforward corrections, and a good reason not to live with it for two years.
Prevention. Correct depth, and a product whose firmness suits the layer. A firm structural gel placed superficially is the usual cause.
Infection
Early bacterial infection, within days, presenting with spreading redness, warmth, swelling and sometimes fever. Managed with antibiotics, and with drainage if an abscess forms.
Herpes reactivation after perioral treatment in someone who carries the virus. This is why a history of cold sores should be asked about, and why prophylaxis is offered to those with a significant history.
Migration and overcorrection
Product moving from where it was placed, most commonly in the lips and tear trough, usually following overfilling or superficial placement in mobile tissue. Overcorrection is the simpler problem.
Both are managed with hyaluronidase where the product is hyaluronic acid, which is, once again, the recurring theme of this section.
Part three: energy-based devices
Burns and blistering, uncommon with correct settings and calibrated equipment, managed as a wound with careful dressing, infection prevention and rigorous photoprotection afterwards.
Post-inflammatory hyperpigmentation, the most common adverse outcome in our skin types. Managed with strict photoprotection, topical treatment, and patience, since it resolves over months rather than weeks. Prevention sits in conservative settings, appropriate intervals and priming the skin.
Hypopigmentation, less common and more serious because it can be permanent. This is the reason we treat conservatively in Fitzpatrick IV and V skin rather than pursuing faster clearance.
Nerve dysfunction, most relevant with focused ultrasound along the jawline, where the marginal mandibular branch is vulnerable. Usually presents as weakness of the lower lip on one side and usually recovers over weeks to months.
Fat atrophy, from energy deposited at an inappropriate depth, producing hollowing that is difficult to correct and sometimes requires volume replacement.
Ocular injury, which is why proper intraocular shields rather than external goggles are required for any work close to the eyes.
Part four: threads
Dimpling and puckering in the first days, frequently settling as swelling resolves, and manageable with massage or release where it persists.
Palpability, where the thread can be felt, usually improving as it absorbs.
Extrusion, where the end works its way towards the surface. Managed by trimming or removing, and the earlier it is addressed the better.
Migration and asymmetry, which may require adjustment or removal.
Infection, which in the presence of a foreign body generally means removing the thread rather than attempting to treat around it.
What a prepared clinic actually has
This is what I would want to know about anywhere I was being treated.
Hyaluronidase in quantity, not a single vial. Managing a significant occlusion uses a great deal, and running out partway through is not a recoverable situation.
A written protocol that someone has actually read, including dosing, repeat intervals and endpoints, accessible in the treatment room rather than in a folder somewhere.
A referral pathway for ophthalmology, with a name and a number, not an intention to look one up.
A referral pathway for plastic surgery.
Photography at baseline, which is how you prove that an asymmetry pre-dated treatment and how you track whether an evolving problem is improving.
Contact details that work outside clinic hours, and someone who answers them.
And a consent process that mentioned these things beforehand. A patient who has never heard the phrase vascular occlusion before it happens to them has been let down twice.
For patients: what to do and when
Go now, do not wait, if you have:
Pain after an injectable that is severe or increasing rather than settling.
Skin turning white, or developing a dusky mottled pattern.
Any change in vision, eye pain, or a drooping lid immediately after treatment. This is an emergency department visit, not a message.
A spreading area of redness with fever.
Contact the clinic within a day or two if you have:
A lump that is new, tender or growing.
Swelling or redness appearing days to weeks after treatment, particularly following an illness or dental work.
A drooping eyelid appearing in the first fortnight.
Asymmetry that is bothering you, since much of it is correctable at a review.
What to bring. What was injected, how much, when, and where. Photographs taken as things changed. If you do not know what was used, say so plainly. It changes the management and nobody sensible will think less of you for it.
And the most important thing: do not accept reassurance that does not match what you are experiencing. Ordinary swelling settles. Pain that is escalating is not ordinary swelling, and the window for treating the serious problem is measured in hours.
The short version
Most complications are minor, temporary and correctable at a review appointment, which is why a review should be part of the plan rather than an optional extra.
A small number are urgent, and of those, vascular occlusion is the one that defines how an injectable clinic should be equipped. It needs recognising within hours, and it needs a quantity of hyaluronidase on the premises rather than a plan to obtain some.
Toxin problems resolve with time, and eyelid ptosis can be managed in the interim while brow heaviness largely cannot, which makes assessment before treatment more valuable than any correction afterwards.
And the complications that become serious are almost always the ones where somebody was reassured instead of examined.
If you have been treated elsewhere and something does not look or feel right, we are happy to assess it and tell you honestly what we think, including when the right answer is a referral. Our account of what we have seen over the years, and the questions worth asking any clinic beforehand, is here.
Book a consultation
Book a consultation with Dr. Kamen Ng at AOKLINIK Penang.
If you are currently experiencing severe pain, skin colour change or any visual symptom after a procedure, please attend an emergency department immediately rather than waiting for an appointment.
Frequently asked questions
Vascular occlusion, where blood supply to an area is interrupted. If the territory connects towards the eye it can cause vision loss. It requires high-dose hyaluronidase urgently, and any visual symptom requires immediate emergency assessment.
Hours for skin, and considerably less for the eye. This is why it matters whether hyaluronidase is physically in the building rather than orderable.
Not reversed, but it can be managed. Prescription eye drops that stimulate a small accessory lid muscle typically lift the lid enough to look normal while the toxin wears off over three to six weeks.
Eyelid ptosis is the lid itself dropping, from toxin reaching the levator muscle. Brow heaviness is the forehead muscle being over-treated so the brow is no longer held up. They feel different, they have different causes, and only the first responds to the eye drops.
Hyaluronic acid filler is dissolvable with hyaluronidase. Calcium hydroxyapatite and poly-L-lactic acid biostimulators are not, and nodules from them are managed with massage, injections and time instead.
It may be inflammatory, or it may be a low-grade bacterial biofilm, and the two look similar. The distinction matters because steroid injected into an infected nodule makes things worse, so it needs assessing rather than treating blindly.
Not on its own, because nothing is resolving. The gel is in the wrong layer. It is readily corrected with a small amount of hyaluronidase.
For bruising, swelling and mild asymmetry, yes, and review at two weeks. For escalating pain, colour change in the skin, or any visual symptom, no. Those are the three that do not wait. ---