BYRYZN — filler or booster
Search for a product introduced as a “skin booster” and the query “BYRYZN filler” comes up alongside it. It is reasonable to be confused. What is written in the approval documents is filler, and the name it is sold under is booster. This piece is not about which of the two is right, but about why both names came to be attached at once and what that fact means for the person having the procedure. To give the conclusion first: “skin booster” is a word that exists as a legal category in no country at all.
The conclusion, first
By its approval it is a filler. BYRYZN is a medical device approved as a tissue-repair biomaterial, and the intended use written on the official site is “to temporarily improve facial wrinkles in adults”. Hydration · skin texture · glow are not in that sentence. And the title of the only paper published on this product is itself the answer — “intradermal hyaluronic acid filler as a skin quality booster” (Yonsei Severance, 2024). That is, a filler used as a booster, not some other thing that is not a filler. “Skin booster” exists as a legal category nowhere in Korea · Europe · the United States — it is a term for a way of injecting. Which is why the US FDA, when approving a product of the same class, created a new indication, “improve skin smoothness of the cheeks”. And written on that approval label is palpable or visible lumps at 63.3% — most resolving within a week, but in 3 people it took 12–15 months before they resolved.
What is written in the approval documents
What is set out on the official BYRYZN site is as follows.
| Main ingredient | Cross-linked hyaluronic acid + lidocaine 0.3% |
|---|---|
| Classification | Medical device · tissue-repair biomaterial |
| Intended use | “To temporarily improve facial wrinkles in adults” (physical repair by subcutaneous injection) |
| Manufacture | Hugel Inc. |
| The number stated | 62026-I10-23-2790, valid until 19 June 2029 |
One thing to point out here. The 62026-I10-23-2790 written on the official site is an advertising review number, not a marketing approval number. An advertising review asks “may this advertising copy be used?”, while a marketing approval asks “may this product be sold?”. Having a validity period attached is also characteristic of an advertising review. The difference between the two numbers is set out in what one line of approval number can and cannot tell you. We too were unable to obtain the original text of BYRYZN's marketing approval number while writing this piece — because the Korean Ministry of Food and Drug Safety (MFDS) medical device database blocks automated lookups.
Hugel's official research and development page introduces BYRYZN under the heading “hyaluronic acid filler”, with the year of approval given as 2021. Which means the manufacturer itself classifies it as a filler.
“Skin booster” is a classification that exists in no country
The term was made in marketing and in clinical practice, and it is entered nowhere in any regulatory framework.
| Jurisdiction | The actual classification | A category called “skin booster” |
|---|---|---|
| Korea | Medical device, tissue-repair biomaterial (class 4) | None |
| Europe | Medical device, Class III (Regulation (EU) 2017/745 Annex XVI) | None |
| United States | Class III; because it remains for 30 days or more it is treated as an “implant” | None |
How the FDA solved this problem
In May 2023, in approving a product of the same class (SKINVIVE by JUVÉDERM), the FDA did not use the existing wrinkle indication but made a new sentence.
“Indicated for intradermal injection to improve skin smoothness of the cheeks in adults over the age of 21.”
— intradermal injection to improve the skin smoothness of the cheeks in adults over the age of 21
So the regulator did not use the words “skin booster” either. Instead it set up a separate indication — not “smooths wrinkles” but “makes the skin smooth” — and specified the site as the cheeks. Those two things are the official description that comes closest to what this product family actually is.
For reference, the definition wavers in the academic literature too. The 2024 paper “Skin boosters: definitions and varied classifications” in Skin Research and Technology is currently marked RETRACTED. We were not able to confirm the original text of the reason for retraction — access to the journal site was blocked, so we confirmed it only from the bibliographic record.
Looked at as material properties — it is not “soft because it is a booster”
There is a study that actually measured the elastic modulus (G′) of products sold as skin boosters under the same conditions. The result is unexpected.
| Product | Cross-linking | HA concentration | G′ (Pa) |
|---|---|---|---|
| Belotero Revive | BDDE chemical cross-linking | 20 mg/mL | 8–13 |
| Viscoderm Hydrobooster | BDDE chemical cross-linking | 25 mg/mL | 33–49 |
| Profhilo | Physical modification only | 32 mg/mL | 40–72 |
| Juvéderm Volite | BDDE chemical cross-linking | 12 mg/mL | 153–165 |
| Restylane Skinbooster Vital | BDDE chemical cross-linking | 20 mg/mL | 489–553 |
All of them are “skin boosters”, and yet G′ spreads from 8 Pa to 553 Pa, a 69-fold gap. A product at a concentration of 12 mg/mL (153–165 Pa) is also more than ten times stiffer than a product at 20 mg/mL (8–13 Pa) — meaning the more concentrated one can be the softer. What the authors confirmed was that what sets the stiffness is not the concentration but the degree of cross-linking.
There is one conclusion to draw from this — the name “skin booster” tells you almost nothing about the substance inside. The differences among products sold under that one name are larger than the difference between a skin booster and an ordinary filler. BYRYZN's measured G′ is not published, so we could not put it in this table.
For ordinary volumising fillers, another study reports G′ of 128 Pa for Belotero Balance, 207 Pa for Juvéderm Ultra XC and 864 Pa for Restylane-L. However, the measurement frequency and strain differ, so those figures cannot be set directly side by side with the table above. Please use only the ordering within each study.
BYRYZN does actually have a paper
Among domestic booster products there are many with no peer-reviewed paper at all. BYRYZN has one.
| Design | Prospective · single-centre · single-arm · open-label pilot (no control group, no blinding) |
|---|---|
| Participants | 20 people, mean age 54.1 |
| Procedure | Intradermal micropuncture injection, 3 sessions at 2-week intervals |
| Follow-up | 12 weeks in total |
| Main result | Lemperle wrinkle scale baseline 2.60 ± 0.60 → week 8 1.55 ± 0.51 (a 40% reduction), with the improvement narrowing to about 33% at week 12 |
| Also measured | Maximum wrinkle height (Rz) · roughness (Ra) · elasticity (R2) · pore area · hydration · transepidermal water loss · gloss — all significantly improved from baseline |
| Adverse events | Transient subcutaneous nodule in 1 of 20. No serious or persistent adverse event was reported |
What to look at alongside this paper
The title is “The efficacy of intradermal hyaluronic acid filler as a skin quality booster”. The researchers themselves framed this as “a filler used as a booster”. And there are three things you should look at with it.
- There is no control group. All 20 received the procedure and there was nothing to compare against. So “it improved because of the procedure” cannot be proved by this design. That is simply what a pilot study is.
- Observation ended while the improvement was already shrinking. 40% at week 8 → 33% at week 12. Beyond that nothing was measured.
- The interval between sessions is 2 weeks. That differs from the 4-week interval commonly quoted in Korea. We did not find a study comparing which of the two is better.
We also note a point where the labelling does not line up. This paper gives the manufacturer of the test product as “ACROSS Co., Ltd., Gangwon-do, Korea”, while the official BYRYZN site gives the manufacturer as Hugel Inc. We were not able to confirm the relationship between the two companies. It may be contract manufacture or a change of company name, and it may be something else. We will not write it down one way or the other while we have not confirmed it.
What happens when it is placed shallow — the material that has numbers
For this product family, the largest set of adverse events disclosed, and in the most reliable form, is the FDA approval label. These are the results of the initial procedure in the US pivotal trial.
| Item | Overall | Mild | Moderate | Severe |
|---|---|---|---|---|
| Any response | 79.4% | 54.3% | 18.6% | 6.5% |
| Lumps · bumps | 63.3% | 47.2% | 12.1% | 4.0% |
| Redness | 68.8% | 57.3% | 9.5% | 2.0% |
| Swelling | 61.3% | 49.7% | 9.5% | 2.0% |
A palpable lump is closer to the rule than the exception. That said, most resolved within 7 days. And the label wrote down the exception as well — in 3 people mild to moderate lumps did not resolve until 12–15 months after the procedure. Adverse events related to the procedure were 3.0%, and of those 76.2% resolved within 30 days.
How you read this number matters. 63.3% does not mean “this is dangerous”; it is closer to meaning “this is simply what this procedure is like”. Put gel into the shallow dermis at many separate points and having it palpable for a few days is the normal course. The question is whether you were told this before the procedure. Experienced without having been told, it becomes a side effect; experienced having been told, it becomes the course.
Rare but long-lasting — delayed-onset nodules
Nodules appearing weeks to months after the procedure are a separate problem. The figures cited by reviews in this field are as follows.
| Prevalence of delayed-onset nodules | 0.8% |
|---|---|
| Restylane inflammatory reactions (after a manufacturing process improvement) | 0.15% → 0.06% |
| Complications of low-molecular-weight HA fillers | 1 – 4.25% |
| Granulomas related to HA fillers | 0.02 – 0.4% |
All four of these figures are secondary citations, and we were not able to confirm the original paper behind each of them. Please take them only as figures cited by a review.
Two sentences written by the same review connect back to the properties table above — “placement of HA within the dermis, particularly in its superficial layer, is associated with an increased risk of granuloma formation”, and “a high-G′ product placed superficially is more likely to be palpable or visible”. The fact that G′ spreads 69-fold between products sold as skin boosters takes on its real meaning here.
Lidocaine 0.3% is not a point of difference
The explanation that “it hurts less because it contains lidocaine” has a basis. It is as well to know two things alongside it.
In a 2024 meta-analysis, HA fillers with lidocaine, compared with those without, gave significantly lower pain (VAS) with a standardised mean difference of −2.47 (95% CI −4.15 to −0.79, p = 0.004). By contrast, there was no difference in the degree of wrinkle improvement (p = 0.36) or in overall adverse events (p = 0.51). Tenderness was slightly lower (RR 0.91, p = 0.002).
- 0.3% is the standard value for this product family. The label of the same-class product approved by the FDA also states HA 12 mg/mL + lidocaine 0.3% w/w. It is not a special formulation but the customary concentration in this field.
- The trials included in that meta-analysis are all trials of deep injection into the nasolabial folds. We did not find a randomised trial verifying lidocaine's pain reduction for the method of injecting at many points into the shallow dermis.
“How long does it last” is really three different questions
| What is being asked | What is known about BYRYZN |
|---|---|
| (1) How long the material remains | There is no data. We did not find imaging data on residual material after a small volume placed in the shallow layer |
| (2) How long the visible improvement was maintained | It was measured only up to 12 weeks (40% at week 8 → 33% at week 12) |
| (3) The duration the manufacturer states | “Longer than a water-glow injection” — there is no comparative clinical trial |
For reference, there is one striking piece of data on point (1). In a review of 33 MRI follow-up cases of volumising filler placed deep in the midface, filler was detected in all 33 of the cases reviewed, and in some the procedure had been 8–15 years earlier (residual rate 84.47% ± 4.43%). However, this is data on deep-layer volumising filler and cannot be carried across as it stands to the method of placing a small volume in the shallow dermis. The reason we set this out here is not to argue that “it lasts a long time” but to make clear that the received idea that “HA all disappears within 3–12 months” has itself never been verified.
Common practice for which we did not find evidence
| Practice | The state of the evidence as we confirmed it |
|---|---|
| 4-week intervals | In the literature the source is a 2010 pilot (19 people, no control group) and a 2013 split-face comparison (30 people). We did not find a trial comparing intervals. The only paper on BYRYZN itself used 2-week intervals |
| A set of 3 sessions | The early studies simply used 3 sessions; they did not show that 3 is superior. A randomised trial comparing 2 sessions with 3 (53 people) is in fact registered, but we were not able to confirm whether its results have been published |
| Maintenance every 3–6 months | We found no supporting literature at all |
| Injecting into “the whole face” | The published clinical trials are mostly confined to the cheeks, and the FDA-approved indication also specifies the cheeks as the site. We did not find a controlled trial verifying uniform full-face injection |
| Massage after the procedure | Some studies did it, but we did not find a study comparing massage against no massage |
| “Less Tyndall effect” | There is no comparative trial. We would add that a 2014 paper raised the question of whether the term “Tyndall effect” itself accurately describes this phenomenon (we were not able to confirm the original text of that paper's conclusion) |
One more thing — the frequently cited criterion that “residual BDDE below 2 ppm is safe” is a value in common use in the academic literature. We were not able to confirm the actual regulatory document (an MFDS notification or an international standard) that set this criterion. So a phrase such as “the MFDS criterion of 2 ppm” is not accurate.
In summary — what is confirmed, what we could not confirm
| Confirmed | BYRYZN's classification on approval is tissue-repair biomaterial and its intended use is “to temporarily improve facial wrinkles” · the manufacturer too classifies it as a “hyaluronic acid filler” on its own page · “skin booster” exists as a legal classification nowhere in Korea · the EU · the United States · the FDA created a separate indication, “skin smoothness of the cheeks”, for the same class · products sold as skin boosters differ 69-fold in G′, from 8 to 553 Pa · the FDA label's lumps at 63.3%, most resolving within 7 days, 3 people at 12–15 months · 1 paper on BYRYZN itself (20 people · 12 weeks · no control group) · lidocaine reduces pain only, with efficacy and adverse events equivalent |
|---|---|
| Could not confirm | The original text of BYRYZN's MFDS marketing approval number · HA concentration · degree of cross-linking · residual BDDE · measured G′ (these are published nowhere) · the relationship between the manufacturer named in the paper and Hugel · that paper's funding source and conflict of interest declaration · injection depth and volume per point · an incidence figure for the Tyndall effect (we did not find one in any primary source) · imaging data on residual material after shallow-layer injection |
| Data pointing the other way | Contrary to the received idea that “HA is absorbed within a few months”, MRI follow-up detected filler from 8–15 years earlier (though this is deep-layer volumising filler) · there are cases where a lower-concentration product is ten times stiffer than a higher-concentration one · the improvement is already shrinking by week 12 |
This is why we wrote this piece. “Filler or booster” looks like word play, but it is in fact the question that sets your expectations. Told it is a booster, you come to expect “the skin getting better”; told it is a filler, you anticipate “it fills as much as was put in, and it may be palpable for a few days”. The approval documents, the only paper and the FDA label all point to the latter. We are not telling you not to have this procedure; we are saying that it is better to have it knowing what it is you are receiving.
Frequently asked questions
Is BYRYZN a filler or a skin booster?
By its approval it is a filler. It is a medical device approved as a tissue-repair biomaterial, and its intended use is “to temporarily improve facial wrinkles in adults”. The manufacturer's official research and development page also places this product under the heading “hyaluronic acid filler”. “Skin booster” is a term for a way of using it, not a type of product — injecting small amounts at many points into the shallow dermis.
Is there not an official classification called “skin booster”?
There is not. No category called “skin booster” exists in the MFDS medical device item classification, in the European Medical Device Regulation (EU 2017/745), or in the US FDA classification. The actual approval is obtained as a medical device for improving wrinkles. The FDA solved this problem in 2023 by creating a new indication, “improve skin smoothness of the cheeks”.
Is the 62026-I10-23-2790 on the official site not the approval number?
No. That is an advertising review number. An advertising review examines “may this advertising copy be used?”, while a marketing approval examines “may this product be sold?”. Having a validity period attached (19 June 2029) is characteristic of an advertising review. We too were unable to obtain the original text of BYRYZN's marketing approval number while writing this piece.
I have a palpable lump after the procedure. Has something gone wrong?
It is the most common course. The FDA approval label for a product of the same class records palpable or visible lumps at 63.3%, and most resolved within 7 days. The label also wrote down the exception — in 3 people they did not resolve until 12–15 months. If it is unchanged after several weeks, or is red and painful, or is growing, that is when you should tell the clinic where you had the procedure.
How many weeks apart should the sessions be?
There is no settled answer. The 4-week interval commonly quoted in Korea hardened out of the protocols used by a 19-person pilot study in 2010 and a 30-person study in 2013, and we did not find a trial comparing intervals. The only paper carried out with BYRYZN itself used 3 sessions at 2-week intervals.
Do I have to have 3 sessions?
We were not able to confirm a study showing that 3 sessions are superior. It became common practice simply because the early studies used 3. A randomised trial comparing 2 sessions with 3 (53 people) is in fact registered, but we were not able to confirm whether its results have been published.
I heard it lasts longer because it is cross-linked hyaluronic acid.
It is true that cross-linking changes the material properties. However, we did not find data measuring how much remains when a small volume is placed in the shallow layer. What has been measured with BYRYZN is only the degree of improvement up to 12 weeks, and even that was already shrinking from 40% at week 8 to 33% at week 12. “It lasts longer than a water-glow injection” is a claim with no comparative clinical trial behind it.
Is it a better product because it contains lidocaine?
It does hurt less — pain was significantly lower in the meta-analysis (p = 0.004). However, there was no difference in the degree of wrinkle improvement or in overall adverse events. And 0.3% is the standard concentration for this product family — the label of the same-class product approved by the FDA states the same concentration. It is common practice, not a point of difference.
So are you saying this product does not work?
No. In the 20-person study, the wrinkle scale · roughness · elasticity · hydration · gloss all improved significantly from baseline. What we are saying is that because that study had no control group, it was not proved as far as “it improved because of the procedure”. That is a different statement from “it does not work” — it means it has not yet been verified to that standard.
So how do I decide whether to have it?
We say two things. First, this is not a procedure that fills volume but one that works on the texture of the skin surface, and for that purpose there is evidence. Second, you should know in advance that being palpable for a few days after the procedure is the normal course. If you still want it knowing those two things, it is a reasonable choice. If the idea that what was injected may be palpable for a few days is uncomfortable for you, that in itself is reason enough.
Who wrote this
Written and reviewed by Lee Chi-Hak, MD, medical director of Miso Clinic in Daegu, South Korea. Every study cited above is given together with its design, its size and the limitations the authors themselves recorded, and where we could not find data, we have said that we could not find any.
| Medical director | Lee Chi-Hak, MD |
|---|---|
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| Reference library | All booster and device references |
References
- BYRYZN's own clinical study — Lee JH, Kim J, Lee YN, Choi S, Lee YI, Suk J, Lee JH. The efficacy of intradermal hyaluronic acid filler as a skin quality booster: A prospective, single-center, single-arm pilot study. Journal of Cosmetic Dermatology. 2024;23(2):409–416. PMID 37705328. Prospective · single-arm · open-label · no control group, 20 people (mean age 54.1), 3 sessions at 2-week intervals, 12 weeks of follow-up. Lemperle wrinkle scale 2.60 ± 0.60 → week 8 1.55 ± 0.51 (a 40% reduction), about 33% at week 12. Transient subcutaneous nodule in 1 person. The manufacturer stated in the paper is “ACROSS Co., Ltd.”, which differs from the official site's statement (Hugel Inc.) — we were not able to confirm the relationship between the two companies.
- FDA approval label — SKINVIVE by JUVÉDERM (VYC-12L) Directions for Use, P110033/S059C, approved 15 May 2023. Composition HA 12 mg/mL + lidocaine 0.3% w/w. Indication, original text: “Indicated for intradermal injection to improve skin smoothness of the cheeks in adults over the age of 21.” Injection method: intradermal microdroplet, points no more than 5 mm apart, 0.01–0.05 mL per point. Injection site responses — any 79.4%, lumps · bumps 63.3%, redness 68.8%, swelling 61.3%. Most resolved within 7 days; in 3 people they resolved at 12–15 months.
- Measured properties of skin booster products — Kleine-Börger L, Kalies A, Meyer M, Kerscher M. Physicochemical Properties of Injectable Hyaluronic Acid: Skin Quality Boosters. Macromolecular Materials and Engineering 2021. Oscillatory rheology at 37°C · 1 Hz. G′ — Belotero Revive 8–13 Pa, Viscoderm Hydrobooster 33–49 Pa, Profhilo 40–72 Pa, Juvéderm Volite 153–165 Pa, Restylane Skinbooster Vital 489–553 Pa.
- Ordinary filler properties (different measurement conditions) — Pierre S, Liew S, Bernardin A. Dermatologic Surgery 2015. 5 Hz · 0.8% strain. Belotero Balance 128 Pa, Juvéderm Ultra XC 207 Pa, Juvéderm Voluma XC 398 Pa, Restylane-L 864 Pa. The measurement conditions differ from the item above, so the figures cannot be compared directly.
- European regulation — Allen J, Dodou K. Current Knowledge and Regulatory Framework on the Use of Hyaluronic Acid for Aesthetic Injectable Skin Rejuvenation Treatments. Cosmetics 2024;11(2):54. “Most injectable dermal fillers are classified as Class III regardless of composition” — Regulation (EU) 2017/745 Annex XVI.
- Korean classification — fillers are medical devices in class 4, ‘tissue-repair biomaterial’. The MFDS advises that a product intended for injection into the skin must be either a medicine or a medical device, and that cosmetics may not be used by injection into the skin.
- Lidocaine meta-analysis — Liu, Shang, Zhu, Shan. Efficacy and Safety of Hyaluronic Acid Fillers With or Without Lidocaine in the Treatment of Nasolabial Folds: An Updated Systematic Review and Meta-Analysis. Aesthetic Plastic Surgery 2024. Pain SMD −2.47 (95% CI −4.15 to −0.79, p = 0.004), wrinkle improvement MD 0.08 (p = 0.36), overall adverse events RR 0.97 (p = 0.51), tenderness RR 0.91 (p = 0.002). The trials included are all deep injection into the nasolabial folds, and are not a verification for multi-point injection into the shallow dermis. We were not able to confirm the number of included trials or the total number of patients.
- Delayed-onset nodules — Convery C, Davies E, Murray G, Walker L. Delayed-onset Nodules (DONs) and Considering their Treatment following use of Hyaluronic Acid (HA) Fillers. Journal of Clinical and Aesthetic Dermatology 2021;14(7):E59–E67. Figures cited by this review — delayed-onset nodules 0.8%, Restylane inflammatory reactions 0.15% → 0.06%, complications of low-molecular-weight HA fillers 1–4.25%, granulomas 0.02–0.4%. All four figures are secondary citations and we were not able to confirm the original papers. Statements from the same review: “placement of HA within the dermis, particularly in its superficial layer, is associated with an increased risk”, “a high-G′ product placed superficially is more likely to be palpable or visible”.
- Long-term persistence — Master M, Azizeddin A, Master V. Hyaluronic Acid Filler Longevity in the Mid-face: A Review of 33 Magnetic Resonance Imaging Studies. PRS Global Open 2024;12(7). Filler detected in all 33 of the cases reviewed, residual rate 84.47% ± 4.43%, with some procedures 8–15 years earlier. This is data on deep midface volumising filler and cannot be applied as it stands to a small volume placed in the shallow layer.
- The main evidence for shallow injection of cross-linked HA — (1) Alexiades M et al., Dermatologic Surgery 2023 (randomised · evaluator-blinded, 202 people, 1-month responder rate 57.9% / 58.3%, p < 0.001, 6 months of follow-up) — we confirmed this only from a secondary summary and did not reach the original text. (2) Kerscher M et al., PRS Global Open 2021;9(12), CPM-HA20G, 159 people — the randomisation in this trial is not a comparison against an untreated control but a comparison of multiple sessions against a single session. (3) Streker M et al., Journal of Drugs in Dermatology 2013;12(9):990, split-face · blinded assessment, 30 people, NASHA 12 mg/mL, 3 sessions at 4-week intervals, 36 weeks of follow-up, improvement on the treated side in more than 80%.
- The source of the 4-week interval · 3-session practice — Reuther T, Bayrhammer J, Kerscher M. Archives of Dermatological Research 2010. Pilot · non-randomised · uncontrolled, 19 people, 3 sessions at 4-week intervals, 16 weeks of follow-up. We were not able to confirm the actual figures and p values, having failed to access the original text.
- The 2-versus-3-session trial — NCT02403986 (Galderma). Randomised · multicentre · open-label · uncontrolled, 53 women, an initial 2 sessions versus 3, 18 months of follow-up, status Completed. We were not able to confirm whether the results have been posted or written up.
- An ongoing untreated-control trial — NCT07047638 (Galderma). Randomised · evaluator-blinded · untreated control · multicentre, about 171 people, injections at weeks 0 / 4 / 8, primary assessment at week 12. Active, not recruiting. Primary completion expected April 2026, final completion expected July 2027 — that is, even the oldest brand in this product family does not yet have results from a blinded trial against an untreated control.
- The retraction of the “skin booster” definition paper — Yi KH et al., Skin boosters: Definitions and varied classifications. Skin Research and Technology 2024;30(3), DOI 10.1111/srt.13627 — the bibliographic record is marked “RETRACTED”. We were not able to confirm the original text of the reason for retraction (access to the journal site was blocked).
- Tyndall effect — Rootman DB, Lin JL et al., Does the Tyndall Effect Describe the Blue Hue Periodically Observed in Subdermal Hyaluronic Acid Gel Placement? Ophthalmic Plastic & Reconstructive Surgery 2014;30(6). PMID 25192332. We confirmed only the title and bibliographic details and did not reach the original text of the conclusion. And we did not find an incidence figure for the Tyndall effect in any primary source — which is why no number for it appears in this piece.
- Residual cross-linker — Fidalgo J et al., Medical Devices: Evidence and Research 2018. “Residual unreacted BDDE below 2 ppm is regarded as non-toxic”. Because we were not able to confirm the actual regulatory document that set this criterion, we have not described it as “an MFDS criterion” or “an FDA criterion”. The same paper also reports that high-temperature alkaline sterilisation produces a by-product of the same mass as BDDE, so the residual amount may be overestimated.
- Manufacturer material — Hugel's official research and development page (classifying BYRYZN as a “hyaluronic acid filler”, with approval given as 2021), the official BYRYZN site (cross-linked hyaluronic acid, tissue-repair biomaterial, the original text of the intended use, the advertising review number). The manufacturer's promotional phrases “minimised Tyndall phenomenon” and “lasts longer than a water-glow injection” are claims with no comparative clinical trial behind them, and have not been used as evidence in this piece.
- What we were not able to confirm — (1) BYRYZN's MFDS marketing approval number · model name · class · the original text of its intended use (automated lookups on the MFDS database are blocked) (2) HA concentration · degree of cross-linking · residual BDDE · measured G′ (these are not published) (3) the corporate relationship between the manufacturer named in the paper and Hugel (4) that paper's funding source and conflict of interest declaration, injection depth, and volume per point (5) whether Restylane Skinboosters is approved in Korea and the wording of its intended use (6) MRI · ultrasound data on residual material after shallow-layer injection.
- The regulatory content of this piece is as of 4 September 2026. Approval details and product information change, so before an actual procedure please check the marketing approval number of the product used directly with the clinic.
Everything in this column is general information and does not replace medical diagnosis or treatment. Effects and side effects vary with individual skin condition, age and underlying illness, and the same result is not guaranteed for everyone. Any decision to proceed should be made in an in-person consultation with a physician.
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