Medically reviewed by Hassan Khan, MPharm — independent prescriber (GPhC registration 1126145). Treatments are carried out by our trained aesthetics practitioner following a prescriber assessment.

Hyaluronic acid: the main ingredient

Hyaluronic acid (HA) is a naturally occurring sugar molecule (a glycosaminoglycan) found throughout your skin, joints and eyes, where its job is to attract and hold water — a single gram can bind several litres. The HA in lip filler is made by bacterial fermentation in a lab, not from animals, and is purified to medical grade. On its own, natural HA would be broken down by your body within a day or two; filler lasts months because of what happens next.

Cross-linking: why filler is a gel, not a liquid

To turn HA into a filler, manufacturers link the chains together — “cross-linking” — using an agent called BDDE, almost all of which is removed or neutralised in processing. The result is a smooth, elastic gel your body still recognises as hyaluronic acid but breaks down slowly, over months rather than hours. Softer, lightly cross-linked gels are used for lips because they need to move naturally when you talk, eat and smile; firmer gels are reserved for structural areas like cheeks, chin and jawline.

What else is in the syringe?

Most reputable lip fillers contain just three things: cross-linked hyaluronic acid, a sterile buffered saline solution to carry it, and lidocaine — a local anaesthetic that makes treatment much more comfortable. Well-known CE-marked ranges used in UK clinics include Juvéderm and Restylane, both of which have decades of published safety data behind them. At your consultation we’ll tell you exactly which product we recommend for your lips and why.

How your body breaks lip filler down

Your body dismantles filler with hyaluronidase — the same enzyme it uses on its own HA — which is why lip filler is temporary, typically lasting 6–12 months. It’s also why HA filler is the reversible option: a clinician can inject pharmaceutical hyaluronidase to dissolve it within days if you’re unhappy or in the rare event of a complication.

Are there fillers not made of hyaluronic acid?

Yes — fillers based on calcium hydroxylapatite, poly-L-lactic acid and other materials exist, and permanent silicone-based fillers were used historically. For lips, we use hyaluronic-acid fillers only: they look and feel natural in a moving area, they’re well studied, and above all they can be dissolved. A filler that can’t be reversed has no place in lips. Before you book anywhere, read is lip filler safe? — it covers the questions any good injector should welcome.

What’s in lip filler: your questions answered

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