What Crosslinked Hyaluronic Acid Is Doing in Your Serum

If your serum promises plumpness that lasts longer than a glass of water, the back label may quietly name a crosslinked hyaluronic acidHyaluronic acidModerateSodium Hyaluronate · GlycosaminoglycanPowerful humectant; molecular weight decides whether it sits on the surface or gets in.Open in the Index → (HA) salt rather than plain HA. Those names look intimidating. The chemistry is more practical than mystical: linear hyaluronate chains are linked into a three-dimensional network so the gel holds water and texture differently on skin.

On 11 September 2026 the Cosmetic Ingredient Review released a Draft Report on six sodium hyaluronate crosspolymers — starting with Sodium Hyaluronate CrosspolymerSodium Hyaluronate CrosspolymerEmergingSodium Hyaluronate Crosspolymer · Crosslinked hyaluronate polymerCrosslinked sodium hyaluronate used as a humectant and skin conditioner; a US safety panel is reviewing it for the first time alongside five related crosspolymers.Open in the Index → (SHC) — for the Expert Panel's 5-6 October meeting. This is the first time the Panel is seeing this family as a formal cosmetic safety assessment. The Discussion and Conclusion sections are still blank in the draft. The October meeting is where the Panel decides whether the data support a Tentative Report, or whether it needs an Insufficient Data Announcement [1] [3].

Crosspolymer versus the HA you already know

HA and its sodium salt are long sugar chains that bind water. CIR has already reviewed those simpler hyaluronates. A 2009 assessment and a 2023 re-review concluded that HA, sodium hyaluronate and several related salts and hydrolysates are safe in the present practices of use and concentration described in those reports [1] [5].

A crosspolymer starts from that same polyhyaluronate backbone and adds chemical bridges between chains. CIR's dictionary definitions say the six ingredients under review share that backbone and differ mainly by which crosslinker is used [1]:

• SHC: vinyl sulfone
• Sodium Hyaluronate Crosspolymer-2Sodium Hyaluronate Crosspolymer-2EmergingSodium Hyaluronate Crosspolymer-2 · Crosslinked hyaluronate polymerCrosslinked HA (diglycidyl ether); in CIR’s first Draft Report on six sodium hyaluronate crosspolymers for the Oct 2026 Panel.Open in the Index → (SHC-2): diglycidyl ether
• Sodium Hyaluronate Crosspolymer-3Sodium Hyaluronate Crosspolymer-3EmergingSodium Hyaluronate Crosspolymer-3 · Crosslinked hyaluronate polymerCrosslinked HA (propylbisoxyamine); in CIR’s first Draft Report on six sodium hyaluronate crosspolymers for the Oct 2026 Panel.Open in the Index → (SHC-3): propylbisoxyamine (after oxidation of the hyaluronate to enable crosslinking)
• Sodium Hyaluronate Crosspolymer-4Sodium Hyaluronate Crosspolymer-4EmergingSodium Hyaluronate Crosspolymer-4 · Crosslinked hyaluronate polymerCrosslinked HA (BDDE (1,4-butanediol diglycidyl ether)); in CIR’s first Draft Report on six sodium hyaluronate crosspolymers for the Oct 2026 Panel.Open in the Index → (SHC-4): 1,4-butanediol diglycidyl ether (often abbreviated BDDE in the medical-filler literature)
• Sodium Hyaluronate Crosspolymer-6Sodium Hyaluronate Crosspolymer-6EmergingSodium Hyaluronate Crosspolymer-6 · Crosslinked hyaluronate polymerCrosslinked HA (PEG-9 diglycidyl ether); in CIR’s first Draft Report on six sodium hyaluronate crosspolymers for the Oct 2026 Panel.Open in the Index → (SHC-6): PEG-9 diglycidyl ether
• Sodium Hyaluronate Crosspolymer-7Sodium Hyaluronate Crosspolymer-7EmergingSodium Hyaluronate Crosspolymer-7 · Crosslinked hyaluronate polymerCrosslinked HA (sodium trimetaphosphate); in CIR’s first Draft Report on six sodium hyaluronate crosspolymers for the Oct 2026 Panel.Open in the Index → (SHC-7): sodium trimetaphosphate

In formula language, crosslinking builds a mesh that can feel more cushiony and can resist rinse-off or evaporation differently from a free-flowing humectant solution. Marketing often calls this "crosslinked HA" or "HA gel." The INCI line is more precise: it tells you which salt and which bridge chemistry the supplier registered.

Important boundary for enthusiasts: injectable dermal fillers that use crosslinked HA are medical devices, not leave-on cosmetics. CIR's cosmetic review is about topical products such as serums, foundations and cleansers. The draft notes that filler literature is sometimes informative for chemistry and for residual crosslinker questions, but the Panel's job here is cosmetic use [1].

What the draft says these ingredients do on a label

According to the International Cosmetic Ingredient Dictionary as summarised by CIR, five of the six are listed as skin-conditioning agents. SHC-2 is listed as a humectant [1]. In a serum you will usually meet them as texture and hydration helpers rather than as a single "active" percentage you can compare across brands.

FDA Registration and Listing Data from 2025, as tabulated in the draft, put SHC in 5,396 formulations: by far the busiest member of the group. SHC-6 appears in hundreds of listings; the numbered variants -2, -3, -4 and -7 are reported far less often [1] [3].

Concentration data submitted to CIR for 2026 identify SHC at up to 0.95% in traditionally applied foundations and in leave-on face and neck products. Other reported maxima in the draft's use tables include moisturisers and cleansers at lower levels, lipstick and lip gloss at up to 0.00035%, and bath soaps and body washes at trace levels. For several of the numbered crosspolymers, frequency of use is reported without a matching maximum concentration from the industry survey [1].

What the Panel is actually reviewing in October

The Scientific Literature Review for this family was posted on 26 March 2026. Industry comments followed in April. A human repeated-insult patch-test summary and updated concentration tables were added before the September draft. October is the Panel's first full reading of the Draft Report [1] [2] [3].

CIR's covering memo is explicit about the fork in the road. If the Panel believes no further data are needed, it should draft a Discussion and issue a Tentative Report. If gaps remain, it should list those needs and issue an Insufficient Data Announcement [1] [3]. Until that vote, any blog that claims the Panel has already "cleared" or "flagged" these crosspolymers is ahead of the document.

The draft itself flags several exposure contexts the Panel will weigh: eye-area products, lip products that can be incidentally ingested, mucous-membrane contact, baby-product listings without complete concentration data, sprays and powders, and airbrush delivery systems. On airbrush use, CIR states that habits-and-practices and particle-size data are not publicly available, so the exposure profile for that delivery route is incomplete and cannot yet be evaluated for safety [1].

What data are already in the packet (without jumping to a verdict)

Polymers of this size are generally expected to sit on the surface of intact skin; CIR notes that dermal absorption of high-molecular-weight crosslinked polymers is typically limited, while residual starting materials such as leftover crosslinker can matter if they remain at meaningful levels [1].

Much of the published toxicology summarised in the draft is not a full classical battery on every numbered INCI. Acute, repeated-dose, developmental, genotoxicity and carcinogenicity studies specific to these cosmetic ingredients were not found for the draft. What CIR did include includes in vitro cytotoxicity work on BDDE- and PEGDE-crosslinked HA gels (materials relevant to Crosspolymer-4 and -6), some immunotoxicity work with BDDE-crosslinked gels in a mouse model, and impurity notes such as a heavy-metal specification for SHC [1].

One human study sits closer to leave-on serum use. An unpublished HRIPT summary provided to CIR tested a serum containing 0.948% SHC in 56 subjects who completed the study. Under the conditions of that occlusive repeated-insult protocol, the report summary states that the product was not associated with skin irritation or allergic contact dermatitis [1]. That is one data point at a concentration near the highest leave-on use reported for that INCI. It is not a finished Panel conclusion for every product category.

The draft also reminds readers that these six ingredients are not restricted under the European Union cosmetic regulation as summarised in the report [1]. Regional rules can change; the Index will track primary sources rather than assume a permanent free pass.

How to read a serum label this week

Look for SHC or one of the numbered crosspolymer names rather than only the front-of-pack phrase "crosslinked HA." If the formula also lists HA or sodium hyaluronate, that usually means free and crosslinked forms are being blended for feel and hydration profile, not that one has secretly replaced the other.

Do not treat medical filler safety stories as a one-to-one guide to a 1% leave-on serum. Different dose, different tissue, different regulatory category.

Watch the October meeting outcome for the first real signal: Tentative Report language, or a list of data the Panel still wants. Either result is more useful than a rumour about whether crosslinked HA is "better" than regular HA. Better for what endpoint, at what percentage, in which product type, is exactly what a safety assessment is for.

FAQ

Is crosslinked HA the same as injectable filler HA?

Not for shoppers. Fillers are medical devices that place a sterile gel into tissue. Cosmetic crosspolymers are ingredient grades used in topical formulas. CIR's October draft is a cosmetic safety assessment, even when it cites filler chemistry papers for context [1].

Did CIR already say these six ingredients are safe?

No. The September packet is a Draft Report. The Discussion and Conclusion are marked to be developed and determined. The Panel meets 5-6 October 2026 to decide the next step [1] [3].

Why do some labels say SHC-4 or -6?

Those numbers mark different crosslinkers on the same hyaluronate backbone. -4 uses BDDE; -6 uses a PEG diglycidyl ether bridge. The feel and supplier grade can differ even when the marketing story still says "crosslinked HA" [1].

Should I stop using my HA serum until October?

Nothing in the draft announces a recall or a use ban. It is a first Panel review of a widely used ingredient family. Ordinary habits still apply: if a product stings beyond a brief adjust period, stop; if you have a known contact allergy, follow your clinician's advice [1].

Bottom line

Crosslinked HA salts are mesh versions of a humectant you already understand, and they are common in modern serums and makeup. CIR's 11 September 2026 Draft Report puts six of them on the October agenda with use counts, concentration tables and early safety data, but without a finished safe-or-not conclusion [1] [3]. The Index entries for HA and each crosspolymer are linked above; treat October's Panel action as the next evidence update rather than a product panic.