What hyaluronidase is and how it works
Hyaluronidase is an enzyme that cleaves the bonds holding hyaluronic acid chains together. The body makes its own version continuously, which is one reason natural hyaluronic acid turns over within days. The injectable pharmaceutical form, long used in mainstream medicine to help drugs and fluids disperse through tissue, does the same job at speed and scale: injected into or around a deposit of hyaluronic acid filler, it starts breaking the gel apart within minutes, with most of the visible change complete over 24 to 48 hours.
Two properties define its clinical character. It works only on hyaluronic acid, so it can do nothing for biostimulatory or permanent fillers such as calcium hydroxylapatite, poly-L-lactic acid or old silicone. And it is a prescription-only medicine in the UK, which means it must be prescribed by a doctor, dentist, prescribing nurse or prescribing pharmacist. That legal fact quietly determines who can safely inject filler at all, because an injector who cannot obtain hyaluronidase cannot manage filler's most serious complication. Our piece on what UK law actually regulates explains that gap in full.
Emergency use versus elective dissolving
The enzyme has two very different jobs.
Emergency use. If filler enters or compresses a blood vessel, tissue downstream begins to die within hours. The treatment is immediate flooding of the area with high doses of hyaluronidase, repeated until circulation returns. In this setting there is no patch test, no deliberation and no waiting; the risk of untreated occlusion vastly outweighs the small risk of allergy. This is why "do you hold hyaluronidase on site" is the single most revealing question to ask any filler clinic, and why the answer must be yes before you are treated, not couriered afterwards.
Elective dissolving. The commoner, calmer scenario: filler that has migrated, lumped, overfilled, tinted the skin blue under the eyes, or simply outstayed its welcome. Here the timetable is measured in weeks and the process is planned, staged and patch tested. Typical referrals include the migration patterns covered in our guide to lip filler migration and the under-eye complications described in our piece on tear trough filler.
Allergy and patch testing
Hyaluronidase is a protein, historically derived from animal sources, and it can provoke allergic reactions ranging from local swelling and hives to, rarely, anaphylaxis. Reported rates of significant allergy are low, in the region of a fraction of one per cent, and higher with repeated exposure. Patients with allergy to bee or wasp venom are treated with extra caution, since venom contains related enzymes.
For elective work, standard practice is an intradermal patch test, a tiny dose in the forearm observed for around 20 to 30 minutes, with treatment either the same day or at a later visit depending on clinic protocol and the amount to be dissolved. A raised, itchy wheal beyond the expected small bump flags a problem. A clinic that skips patch testing for non-urgent dissolving is trimming a safety step to save an appointment slot, and it is reasonable to ask why.
In an emergency, hyaluronidase is given without a patch test, because dying tissue outranks a rash. Electively, there is no such excuse for skipping it.
What a dissolving appointment involves
After assessment, sometimes with ultrasound to map where product actually sits, the area is cleaned and the enzyme injected into and around the filler deposits, often with gentle massage to spread it. The injections sting more than filler does, and the area typically swells immediately, partly from the fluid volume, which alarms patients expecting instant deflation. Over the next day or two the swelling settles and the gel breaks down.
Expect the treated area to look worse before better: swollen for a couple of days, then deflated, sometimes slightly crepey or empty-looking for a week or two while skin retracts and the body clears debris. Lips in particular can look startlingly flat. This phase passes, and judging the result before two weeks is judging it too early.
How much dissolves, and does it affect your own tissue
One session of adequately dosed hyaluronidase can dissolve most of a recent, accessible deposit of standard hyaluronic acid filler. In practice, complete clearance in one visit is not guaranteed. Older product develops a degree of resistance as it integrates with tissue, heavily cross-linked fillers break down more slowly, and stacked layers from years of treatment may need two or three sessions spaced a fortnight apart. Some practitioners deliberately under-dose to dissolve partially, preserving some volume, though the precision of partial dissolving is more art than science and results are less predictable than patients are told.
The enzyme also degrades your own hyaluronic acid, which sounds alarming and largely is not. Native hyaluronic acid regenerates within days, and studies and long clinical experience in medical uses of the enzyme have not shown lasting tissue damage at appropriate doses. The transient deflated look owes more to losing the filler's volume and water than to any loss of your own tissue. What hyaluronidase cannot do is undo stretch: skin expanded by years of large volumes may not fully snap back, particularly in older patients.
Retreatment and refilling timelines
Repeat dissolving sessions are usually spaced about two weeks apart, long enough to see what remains once swelling clears. Refilling follows the same logic: a minimum of two weeks after the final dissolving session, and many careful practitioners prefer four. The enzyme itself is inactivated in tissue within days, so the wait is not about protecting new filler from destruction; it is about injecting into settled tissue and making decisions off your true baseline rather than a swollen one.
It is also, frankly, a natural pause for reflection. A meaningful minority of patients who dissolve, particularly lips, decide once the swelling settles that their natural anatomy needs less correction than they had assumed.
Cost and where to have it done
Observed UK pricing in 2026 runs from roughly £150 to £350 per dissolving session, with complex or ultrasound-guided work above that, against the wider ranges in our 2026 price survey. Because hyaluronidase is prescription-only, the person treating you must either be a prescriber or working to one who has seen you. Dissolving is also more technically demanding than it sounds, particularly around the eyes, so this is work for an experienced medical practitioner, verifiable through the GMC, NMC or GDC registers, or an accredited scheme such as the JCCP. The clinic that injected the original filler is not automatically the right place to dissolve it, especially if its assessment of the problem differs from yours.