11th November 2022

3 Scary Complications Of HA Fillers: Two Can Be Mitigated With Hyaluronidase

Last Modified: November 12, 2022

Since the approval of the first hyaluronic acid (HA) filler in the United States in December 2003, HA fillers have become a mainstay of soft tissue augmentation due to their favorable safety profile and minimally invasive treatment nature.

Even here in the UK, HA fillers have become one of the most popular non-surgical cosmetic treatments, a close second to wrinkle-relaxing injections aka Botox.

While these fillers are effective and generally well tolerated by most patients, in an industry that continues to experience record growth rates, complications associated with HA fillers are bound to occur.

Fortunately, more than 90% of complications associated with the use of HA fillers are mild and temporary. These include redness and swelling at the injection site.

However, for more serious consequences, certain treatments can be attempted, the leading being hyaluronidase injections.

This article addresses the complications of HA fillers, along with methods of prevention and management as well as when hyaluronidase is and is not effective.

Tyndall Effect

Occasionally, HA filler can lead to a phenomenon known as the Tyndall effect.

In the medical aesthetics field, the Tyndall effect is used to describe the bluish hue that is visible in the skin due to the superficial placement of hyaluronic acid (HA) filler.

The basic principle behind the Tyndall effect is that different wavelengths of light are scattered differently depending on the size of the substance they encounter.

For example, blue light is scattered about 10 times more than red light when it passes through very small particles in the air. This is the reason why the sky appears blue.

A similar thing occurs when the fine molecules of HA placed right beneath the skin scatter more light of shorter wavelengths, resulting in a bluish discoloration.

This can easily be mistaken for a slight bruise. But there is a crucial difference: unlike a bruise, this one does not disappear after a few days!

The more small particles the filler contains, the greater the scattering and the more pronounced the discolouration.

The thinner the skin in this area, the greater the risk that the Tyndall effect will occur. This is why complication occurs more frequently under the eyes and in the mouth area.

The bottom line is that the Tyndall effect is usually due to incorrect product placement by an inexperienced practitioner.

Of course, to avoid this complication, you must work with an injector who can carefully evaluate your skin and develop an appropriate treatment plan.

The proper technique (e.g., depth and angle of injection) are fundamental to preventing this complication from occurring.

If the effect is noticed at the time of treatment, a gentle massage of the area may be sufficient to disperse the superficially placed filler. If the effect is not noticed until later, the only option is to dissolve the HA with hyaluronidase.

This should resolve the problem within 24 hours, although occasionally a second treatment may be required.


Haematoma (definition): An accumulation of free blood anywhere in the body, that has partially clotted to form a semi-solid mass. Haematomas may be caused by injury or may occur spontaneously as a result of a bleeding or clotting disorder.

One of the most common and lesser severe complications (at least when compared to the next)  associated with HA fillers is the formation of a hematoma (a large swollen bruise). Even with careful protocol, bruising may occur.

The skin on the face is very thin and has prominent vasculature.

An accidental puncture of a blood vessel can immediately cause bleeding, which can result in a bruise. Sometimes, however, bleeding can be delayed due to swelling of the surrounding tissue.

A big challenge posed by haematoma formation is bruises are unsightly and draw attention, especially if they are on the face where they are often difficult to conceal.

This is especially true for men, where the use of concealers and makeup is usually not feasible. 

Read: Facial Masculinisation with Fillers

The initial purple color (due to the presence of deoxyhemoglobin) usually changes over time as the heme group is broken down - first to biliverdin (green), then to bilirubin (orange-yellow), and finally over the course of days to weeks as the bilirubin binds to albumin and is transported to the liver for recycling.

To reduce the risk of bruising during filler injections, several techniques can be employed. Prior to the procedure, some injectors advise their patients to discontinue non-essential blood thinning medications such as aspirin unless they are taking them for therapeutic purposes.

Vitamins and herbs that are associated with an anticoagulant effect (such as vitamin E, ginseng, garlic, ginger, ginko biloba, and fish oils), fall in this category. 

During the treatment, our injectors will carefully monitor the treatment area for signs of bleeding. In case of bruising, it is recommended to apply pressure for 4-5 minutes.

The use of an ice pack is helpful as it constricts the blood vessels and minimizes the risk of the bruise spreading.

At Dr Aesthetica we use blunt-tip cannulas in many of our HA filler treatments to reduce the risk of traumatising a blood vessel.

Read: Sharp Needles vs. Blunt Cannulas

Another possible method that has been suggested to reduce the likelihood of hematoma formation is to discontinue antithrombotics such as NSAIDs and antiplatelet medications, but this is controversial due to the associated risk of embolism or thrombosis.

Before taking any drastic decision, always consult your physician.

Vascular Complications

A vascular occlusion occurs when blood is no longer able to pass through a blood vessel. It may be a complete occlusion or partial occlusion, resulting in a diminished blood supply.

A vascular occlusion may be caused by an internal obstruction, such as a blood clot, a foreign body, such as filler material, or occur as a result of external compression.

If left untreated, a vascular occlusion of a blood vessel supplying the skin can result in skin necrosis and vision loss. This is one of the most alarming complications of treatment with fillers.

To our knowledge, an accurate calculation of the risk of vascular occlusion from filler treatment has never been performed because the probability is very low and the data on the exact number of injections done is generally unavailable. 

However, if one of these vascular occlusions does occur, it can be devastating to the patient if not treated promptly.

Skin Necrosis

A rare complication, skin necrosis, may be caused by accidental injection into an artery or vein, external compression of the vessel by the filler, or direct trauma to the vessel wall by the needle. Patients usually first experience severe, persistent pain and blanching of the skin (it becomes paler than the surrounding area).

This is followed by livedo reticularis (dusky blue-red discoloration). Later signs include necrotic areas, small white blisters, and tissue death.

Venous compression occurs slowly and gradually over several hours, and its symptoms may not appear immediately after the treatment.

In contrast, arterial embolic obstructions caused by HA fillers usually present with symptoms immediately post-injection.

The go-to treatment involves hyaluronidase, which dissolves the filler. Gentle massage can be performed to assist in the distribution of the enzyme.

That's why every qualified injector always has hyaluronidase on hand for HA filler treatment, no matter their patients' satisfaction rate. This is also why we prefer HA fillers over other types, as they are reversible in case of complications.

Vision Loss

The most devastating vascular complications of HA filler injections are stroke and vision loss. This occurs due to arterial occlusion when the filler flows retrograde (backward) into the arterial system. 

Specifically, if the filler is injected too quickly and forcefully, it may encounter less resistance due to retrograde flow into the vessels.

In particular, the periorbital area around the eyes is vulnerable to vascular events due to its anatomy. The ophthalmic artery is a large vessel with many branches that project to areas outside the ocular area on the nose and forehead.

These branches anastomose with other arteries in the face, which explains why intravascular injections at sites far from the eye can still result in visual loss.

The injection sites at the highest risk for ocular complications are the glabella, nasal region, nasolabial fold, and forehead.

Fortunately, intracerebral stroke or loss of vision as an adverse consequence of HA fillers is extremely rare, with only a few hundred occurrences reported over the years. In fact, many of the cases of blindness due to injectable aesthetic treatments have been associated more with autologous fat injections.

Because HA molecules are structurally much smaller than fat, they are more likely to penetrate further into the vascular system.

As a result, the smaller distal branches of the ophthalmic artery become occluded  (less risk) as opposed to the larger ophthalmic or central retinal arteries.

As you can imagine, treating vascular complications is not straightforward. 

The first and most important step is to minimise the risk of vascular occlusion in the first place.

The injector should have detailed knowledge of the three-dimensional anatomy of the area to be treated.

They must also understand the distribution and depth of vessels of the target areas and possible variations thereof. Nothing replaces working with an experienced and knowledgeable technician.

Some techniques they use include (these may be good question points for your injector during the consultation):

  • Aspiration prior to injection
  • A slow injection technique under low pressure 
  • Minimum filler volume with booster treatment after two weeks
  • Avoidance of highly vascularised areas
  • If something goes wrong, they should know exactly what to do and take remedial action as soon as possible. Among the measures that can be taken are:

The injection must be stopped immediately if there is any suspicion of vessel blockage.

Massage the area firmly while applying heat to promote vasodilatation.

Rapid use of hyaluronidase has been shown to be highly effective and may help prevent tissue necrosis.

There is research showing that high-frequency ultrasound can help pinpoint the location, depth, and size of the filler embolus. This further increases the success rate of hyaluronidase.


Potential complications are not completely avoidable for even the most skillful and experienced injectors. Fortunately, the incidence of adverse events is low and the vast majority are mild in nature.

Also, truly catastrophic complications, such as skin necrosis and vision loss can be prevented with awareness of underlying facial anatomy and well-thought-out injection techniques.

There's no doubt that HA filler injections can provide excellent results when properly performed. Fill out a consultation form here, or call us at 0121 769 0242. We will be happy to answer any questions you may have if you are considering getting a dermal filler treatment.

And always remember that the ideal skincare regimen should not be one size fits all. It needs to be tailored to fit you and not the other way around.

Post Reviewed by: Dr Baldeep Farmah
Medically Reviewed on: 11th November 2022
Dr Baldeep Farmah is the Medical Director and lead Doctor of Dr Aesthetica, a Medical Aesthetic Clinic.

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