What hyaluronic acid injection can and cannot do. The strength of being able to dissolve it and its limitations

Hyaluronic acid injection is a procedure that places gel-like hyaluronic acid, which retains water, under the skin to fill in depressions and wrinkles and add contour[1]Results appear immediately after injection and typically last approximately 3–12 months depending on the area and formulation[1][2]The greatest strength is that it can be dissolved and reversed with an enzyme called hyaluronidase[3]On the other hand, if it enters a blood vessel, it can cause complications leading to skin necrosis or blindness, which falls outside the scope of what can be reversed[4].

What can be accomplished with hyaluronic acid injection?

What can be done is adding missing volume. Textbooks explain that hyaluronic acid is a negatively charged polysaccharide that attracts water to create volume and support[1]It is used for fine wrinkles, lips, depressions under the eyes (tear trough), and mild contouring, injected from shallow layers to the mid-dermis, typically in one session (with touch-ups if needed), and results appear immediately[5].

It is also the most commonly used injectable agent around the eyes, and ophthalmology textbooks state that when injected below the orbicularis oculi muscle it is effective for 3–12 months[2]There are also ways to use it to raise the nasal bridge, and consensus documents for Asian populations have been compiled[3].

What cannot be done?

Making major shape changes and making it permanent are not possible. In injectable agent comparison tables, hyaluronic acid is indicated for use only up to mild contouring[5]Hyaluronic acid is a temporary injectable[6]In a 18-month follow-up comparative study, although effects from a single injection remained at 18 months, they decreased over time[7].

In the nose, complications from injection can make subsequent surgery difficult, and cases may require skin or cartilage grafting, according to consensus documents[3]This is a point to understand before thinking 'I'll try it casually and have surgery if it doesn't work'[3].

How long does it last?

The standard is 3–12 months, varying by formulation and area[1][2]Injectable agent comparison tables show 6–12 months[5]Textbooks note that in areas with minimal movement, it may remain for 10 years or more[1]Indeed, granulomas (masses formed as a reaction to foreign bodies) from hyaluronic acid injected 10 years ago have been reported, and even 'dissolved' material may persist[6].

Polylactic acid (PLLA), a type that stimulates collagen production, has a delayed onset of 6–12 weeks and lasts 18–24 months, according to the same comparison table[5]The difference is that hyaluronic acid works quickly and is reversible, while PLLA works slowly and lasts longer[5].

How true is it that it can be dissolved?

It is true, but it is not a panacea. Hyaluronidase, an enzyme, breaks down hyaluronic acid and is used to address overfilling, uneven distribution, and vascular occlusion[8]。The consensus document lists this 'reversible medication exists' as a strong recommendation based on moderate-quality evidence[3]。Calcium-based fillers without a corresponding reversal agent also become a reason why nasal injection is not recommended[3].

。However, formulations with strong Cross-linking (processing that connects molecules for longevity) are difficult to dissolve and may require multiple treatments every 3 weeks[9][8]。In long-lasting formulations resistant to enzymes, excision is considered, the review states[9].

Non-reversible complications? When it enters blood vessels

The most serious complication is vessel occlusion[4]。When hyaluronic acid enters a blood vessel or compresses it, skin necrosis and blindness can occur[4]。When it enters an artery, tissue damage, scarring, vision loss, and even cerebral infarction can occur, according to a 2026 review[10].

When it occurs, the course is rapid, with skin color changes within hours and necrosis or ulceration visible within 24 hours[9]。The standard response is to quickly inject hyaluronidase to restore blood flow[11]and if there is no improvement within 60 minutes, a protocol of repeating additional injections up to 4 times maximum is introduced[4]。There is also a report of recovery with minimal scarring after 90 days despite delayed consultation 3 days later and 32,000 units total administered over 4 days, but the author states that the later the consultation, the higher the risk of necrosis[11].

Nasal injection is positioned as a 'high-risk procedure' with risks of skin necrosis and blindness, and the consensus document states it should only be performed by experienced injectors[3]。Although rare in frequency, multiple reviews repeatedly emphasize that thorough knowledge of facial blood vessel anatomy reduces risk[4][10].

Mild side effects and delayed reactions

Most side effects are mild, temporary, and reversible[4]Early-onset reactions include redness, swelling, bruising, nodules, whitening of the skin, and infection[3]Delayed-onset reactions include granulomas, filler migration, and delayed hypersensitivity reactions[3].

Rarely, hair loss has been documented in 19 cases in the literature following injection into the forehead or temples[12]Sterile abscess (abscess without bacteria) is also a relatively newly recognized complication[13].

What to confirm at your consultation

What you want to confirm is whether your concern is the type that can be solved by adding volume, which layer to inject which product into and how much, and whether hyaluronidase can be used immediately in case of emergency[3][4]In areas with high risk of vascular occlusion, such as the nose and around the eyes, you should also confirm the experience of the injecting physician[3].

Always inform the doctor of the type and timing of any fillers you have had injected in the past. There have been cases where filler from 10 years ago remained[6]because with products that do not dissolve easily, the number and method of treatments may change[9]How much volume to add for a natural result, and whether methods other than adding volume are better, will be decided at your consultation after examining your entire face