How Fillers Work

The tissue of the skin and subcutaneous tissue is composed of factors including cells, collagen and elastin that is held within a matrix of hyaluronic acid. Pharmaceutical companies have manufactured hyaluronic acid that is injectable and stays in the tissues for months or years. These manufactured substances are known as dermal fillers and also include products made from calcium hydroxylapatite and poly-L-lactic acid.

Fillers are classed as medical devices, not drugs. They therefore do not require a prescription so beware – they may be acquired by persons who do not have medical knowledge or qualifications. Fillers are injectable gels that add volume to the tissues. Multiple injections are usually required at each treatment session (using needles or cannulae i.e. blunt needles) to sculpt the tissues to the required shape, configuration and volume.

In general terms cosmetic fillers are durable, but not permanent (lasting from a few months to 2-4 years or more depending on the product), well tolerated and some (i.e. hyaluronic acid fillers) are potentially reversible in the event of unfavourable clinical outcomes.

Hyaluronic acid fillers such as Juvederm Smile™ and Juvederm Ultra3™are usually degraded and removed by the body over a 6-12 month period after injection. New generation fillers such as Voluma™, Volift™ and Volbella™ mesh with the body’s tissue rapidly to feel natural within a week or two. Voluma™ may last 18 months in most circumstances or 2-3 years for some people for example a nose job or rhinoplasty. There is evidence that such filler material may remain in the tissues for several years.

When injected the filler material expands the tissue by a direct volume effect. Most hyaluronic acid fillers including the Juvederm and Voluma/ Volbella/ Volift range have a small amount of local anaesthetic (lidocaine/ lignocaine) in them so to minimise discomfort on injection.


Early complications of injecting fillers, including hyaluronic acid fillers, include swelling, bruising, haematoma formation (collection of blood), pain and infection. Complications occur from the time of injection to about 2 weeks and are usually absent by 3 weeks. More serious complications such as skin necrosis (skin death) and blindness can also occur rarely. These serious side effects are more likely if the person injecting the filler has little practical experience of injecting fillers, and poor knowledge of anatomy.

Late complications of injecting hyaluronic acid fillers include lumps (granulomata), delayed hypersensitivity reactions (pain, redness, swelling, lumpiness), and biofilm (accumulation of micro-organisms within a self-developed matrix). Biofilms are not usually identifiable by culture and may appear as sterile abscesses or cause a chronic inflammatory response. This response may flare up and subside in a cyclical fashion. The filler material cannot be metabolised normally when a biofilm is present.

A foreign body immune response and development of biofilm is possible with all fillers. This would be more likely for example when the injection is not as clean as possible. This manifests as pain, soft tissue swelling, oedema (fluid collection) and erythema (redness).

Treatment for biofilms is Hyalase® injected into the area affected. Contemporaneous treatment with oral broad-spectrum antibiotics is indicated for 2-6 weeks. As Hyalase® is a prescription only medicine (POM) it would be wise to only attend medically qualified practitioners for filler treatments.

The majority of the late-onset adverse effects are inflammatory and immune-mediated in nature, and can occur many months or even years after administration of the filler.
All known fillers present on the market for long enough have been shown to be able to provoke early- and late-onset inflammatory adverse reactions and range from local to systemic. Their true prevalence is unknown but appears to be significant. Sometimes surgery is indicated.

If filler material is accidently injected into a blood vessel there is a risk of blindness and skin necrosis (skin death) that may require skin grafts and would result in scarring and facial disfigurement. The treatment is immediate injection into the affected area using Hyalase®, repeated as necessary, and advice sought from an expert. Hyalase® is also indicated in the non-acute setting to dissolve hyaluronic acid fillers if the desired result is not achieved. All practitioners injecting hyaluronic acid filler should have immediate access to Hyalase® or to someone who can safely, knowledgeably and effectively administer Hyalase®.

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