Skincare Ingredients

Sargassum Filipendula Extract

Sargassum filipendula extract is a brown seaweed botanical used at low concentrations primarily for antioxidant/soothing and film-forming benefits rather than as a high-potency active. Clinical irritation risk is generally low, but as a complex marine botanical (with variable polysaccharides, proteins, and trace components), it can still trigger stinging or dermatitis in a minority of highly reactive or eczema-prone patients, so it cannot be scored as exceptionally gentle or inert. Safety Notes: In commercial skincare, Sargassum filipendula (brown algae) extract is most often used as a minor supporting botanical in multi-extract blends or “marine complex” systems, where the effective at-use level can be as low as ~0.001–0.05% (especially in rinse-off cleansers and broadly fragranced/marketing-driven formulas). In leave-on serums, masks, and moisturizers positioned around “seaweed/algae” benefits, it is commonly formulated around ~0.1–2%, with a small number of consumer-available high-strength or single-hero botanical gels/ampoules reaching ~3–5% depending on extract form (glycerin/water carrier, dry extract, or standardized solution) and sensory/stability limits.

Saxifraga Sarmentosa Extract

Saxifraga sarmentosa extract is a botanical skin-conditioning/brightening extract typically used at low concentrations (often <1–2%), but like many plant extracts it contains a complex mixture of polyphenols and other bioactives that can trigger irritation or allergic contact dermatitis in reactive skin. Robust large-scale clinical irritancy data are limited, so I score it as mild rather than “gentle,” especially for eczema-prone patients where cumulative exposure to multiple botanicals increases the risk of stinging, redness, or delayed sensitization. Safety Notes: In commercial brightening/anti-spot leave-on products (serums, emulsions, masks) Saxifraga sarmentosa extract is commonly used as part of multi-botanical complexes, where it can appear at very low labelable levels (~0.001–0.05%) depending on the supplier’s extract strength and whether it is within a blend. Dedicated botanical-brightening formulas and some Asian-market products using higher botanical loads can push the extract itself into the ~1–5% range, with 5% representing the upper end typically seen in OTC consumer leave-on products due to stability, odor/color impact, and cost; rinse-off products tend to sit toward the lower end.

Scenedesmus Deserticola Ferment Extract

Scenedesmus deserticola ferment extract is a biofermented microalgae-derived skin-conditioning/antioxidant ingredient typically used at low concentrations (generally well under a few percent) and is not pH-dependent like exfoliating acids. There is no strong clinical signal that it is a common primary irritant, but as a ferment/biologically complex extract it can provoke stinging or reactivity in a minority of highly sensitized or barrier-impaired users (e.g., active eczema), so it is best categorized as very gentle rather than exceptionally inert. Safety Notes: In commercial products this microalgae ferment extract is often supplied as a diluted carrier-based ingredient and is used at very low levels (around 0.001–0.05%) in mass-market leave-on creams/serums primarily for claims support and marketing positioning. More performance-driven leave-on products (anti-pollution/anti-aging/barrier care) commonly use it around 0.1–1% when the supplier’s recommended use level is followed. A small number of high-claim consumer-available serums/ampoules use it at elevated levels up to ~3%, which is near the practical upper end before texture, odor/color, and formula stability become limiting; rinse-off products typically sit at the low end due to brief contact time.

Schisandra Chinensis Fruit Extract

Schisandra chinensis fruit extract is primarily used as an antioxidant/soothing botanical at low concentrations, but as a complex plant extract it contains multiple bioactive compounds that can provoke stinging or dermatitis in reactive or eczematous skin. Human data are less standardized than for single-molecule ingredients, and botanical extracts have a non-trivial rate of irritation/sensitization on patch testing in sensitive populations. Given the uncertainty in composition between suppliers and the higher risk profile for compromised barriers, I rate it as mild irritation potential. Safety Notes: In mass-market leave-on skincare, Schisandra Chinensis Fruit Extract is often used as a minor botanical/antioxidant component at very low levels (around 0.001–0.05%), especially in complex multi-extract blends where it functions primarily for marketing/label support. Dedicated “K-beauty/clean beauty” antioxidant serums, ampoules, and calming creams commonly use 0.1–2% when the extract is a clear hero ingredient, and a small number of high-strength consumer products (typically leave-on serums/ampoules using standardized extracts) reach ~3–5% where sensorial color/odor and irritation risk become practical limiting factors; rinse-off products generally sit toward the lower end due to short contact time.

Schizophyllan

Schizophyllan is a high–molecular weight beta-glucan polysaccharide used mainly as a film-forming humectant/soothing polymer at low levels (typically well under a few percent) and is not pH-dependent or inherently exfoliating. Available safety and patch-test experience with similar beta-glucans suggests a low rate of irritation and good tolerability even in compromised skin, though rare hypersensitivity to fungal-derived polysaccharides can occur. Given the generally excellent tolerability but non-zero sensitization potential in highly reactive/atopic individuals, a very gentle score is most consistent with patient-safety benchmarking. Safety Notes: Schizophyllan (a high-molecular-weight beta-glucan polysaccharide) is used in commercial skincare primarily as a film-forming, soothing, and hydration-support polymer, often at very low levels (around 0.0005–0.05%) in leave-on serums/creams where it functions as a sensorial and barrier-support additive alongside humectants. More dedicated “beta-glucan/schizophyllan” soothing or post-procedure-style OTC products and some concentrated gel/serum formats push into the 0.1–0.5% range, with the highest consumer-available formulations observed around ~1.0% (higher levels are limited by viscosity/texture, potential tack, and raw material cost rather than specific cosmetic-regulatory caps). Rinse-off use is less common and typically lower than leave-on because contact time is brief and high polymer levels can negatively impact foaming and rinse feel.

Sclareolide

Sclareolide is a fragrance-related aroma compound (often used as a fixative in perfuming) and is typically present at low concentrations, but fragrance materials have a well-documented pattern of causing irritation or contact allergy in sensitized or eczema-prone individuals. While not among the most notorious fragrance allergens, its function and use-context (leave-on products, cumulative exposure with other fragranced items) justify a mild irritancy rating to protect highly reactive skin. Safety Notes: In commercial skincare, sclareolide is most often used as a low-dose odor modifier/skin-feel enhancer in fragranced emulsions and cleansers, with the lowest observed levels around 0.0005–0.005% (5–50 ppm) in leave-on and rinse-off formulas. Higher-dose uses occur in some “odor-control/deodorizing” body products and fragrance-forward lotions/serums where it functions as a fixative/active-like sensory component, reaching about 0.05–0.2% in consumer-available leave-on products. Levels above ~0.2% are uncommon in OTC skincare due to odor impact and sensitization/IFRA-style perfumery constraints, rather than a specific cosmetics-regulatory maximum.

Sclerocarya Birrea Seed Oil

Sclerocarya Birrea (marula) seed oil is an emollient lipid used at relatively high levels in moisturizers and facial oils, and it is generally well-tolerated and non-stinging because it does not rely on low pH or keratolytic activity. However, like other botanical oils it can still trigger irritation or allergic contact dermatitis in a small subset of highly reactive or eczema-prone patients due to natural minor constituents and oxidation byproducts, so I rate it as gentle rather than “very gentle.” Safety Notes: In commercial skincare, marula oil is frequently used at very low levels (~0.05–0.5%) as an emollient/marketing oil within creams, lotions, cleansers, and serums where it is one of many oils and the formula cost/feel is balanced. Mid-range leave-on moisturizers and facial oils commonly use ~1–20% to materially impact sensory feel and barrier support. The upper end reaches 100% in consumer-sold, single-ingredient marula oil products (neat oil), with many “pure marula oil” facial oils falling in the ~95–100% range; no specific global maximum is set for this non-restricted cosmetic ingredient beyond general safety and labeling requirements.

Sclerotium Gum

MVP Approved - Sclerotium Gum is a natural fungal-derived polysaccharide used primarily as a thickening and stabilizing agent in cosmetic formulations, and it is well tolerated by most skin types.

Scutellaria Baicalensis Root Extract

Scutellaria baicalensis (baikal skullcap) root extract is primarily used as an antioxidant/soothing botanical (baicalin, baicalein) and is typically included at low percentages in leave-on products, where it is generally well-tolerated in clinical and consumer use. However, as a complex plant extract, it carries a small but real risk of irritation or allergic contact dermatitis in highly reactive or eczema-prone individuals, especially in compromised barriers or when combined with multiple other botanicals. Given the low typical concentrations but non-zero sensitization potential inherent to botanicals, a gentle (not exceptionally gentle) score is the safest clinically-aligned assessment. Safety Notes: In mass-market leave-on products (toners, emulsions, multi-extract serums) Scutellaria Baicalensis Root Extract is often used as a minor botanical/soothing component at ~0.001–0.05%, reflecting typical supplier use-level guidance and cost/odor/color constraints. Dedicated “brightening/anti-redness” botanical serums, ampoules, and some K-beauty style formulations use it at materially higher levels, commonly ~0.5–2% and occasionally up to ~5% in high-strength consumer products, with the upper end more feasible in leave-on systems using standardized extracts and solubilization to manage polyphenol-related stability and color. Rinse-off products generally sit toward the lower end due to short contact time and budget allocation, while the highest observed levels are predominantly leave-on concentrates.

Scutellaria Galericulata Extract

Scutellaria galericulata (skullcap) extract is a botanical antioxidant/soothing agent typically used at low concentrations (often <1–2%) and is generally well-tolerated in leave-on products. However, like many plant extracts, it contains multiple bioactive compounds that can trigger irritant or allergy-type reactions in a minority of highly reactive or eczematous patients, especially with compromised barrier skin. Given this non-zero sensitization potential but overall low clinical irritancy at typical use levels, it fits best as a gentle (not exceptionally gentle) ingredient. Safety Notes: In commercial skincare, Scutellaria Galericulata Extract is most often used as a minor botanical antioxidant/soothing component in complex blends, where it commonly appears around 0.001–0.1% (especially in mass-market leave-on lotions/serums and rinse-off cleansers). Higher-strength consumer products marketed around “skullcap extract” actives or botanical concentrate serums/masks can reach ~1–5% when the extract is a standardized, solvent-based or dry extract equivalent; levels above this are uncommon due to solubility, color/odor impact, and rising irritation/sensitization risk. There is no specific FDA/EU maximum limit for this plant extract, so the upper end is primarily constrained by supplier guidance and formulation aesthetics/stability, with leave-on products typically formulated lower than rinse-off at comparable claims.

Sd Alcohol 40

SD Alcohol 40 (denatured ethanol) is used primarily as a solvent and penetration enhancer, often at moderate-to-high levels in leave-on products where it can rapidly strip lipids and increase transepidermal water loss. Clinical experience and patch-test/irritant data consistently show it can provoke stinging, erythema, and barrier disruption, with markedly higher risk in eczema, rosacea, and compromised/post-procedure skin. Because it can also amplify irritation from other actives in a routine, I score it high for patient safety in sensitive populations. Safety Notes: In commercial skincare, SD Alcohol 40 (denatured ethanol) is used at very low levels (~0.1–1%) as a solvent/processing aid or to help solubilize fragrance/actives in creams and toners, and at moderate levels (~5–30%) in astringent toners, acne products, and fast-drying gels/sprays. High-strength consumer-available hand-sanitizer gels/sprays and antiseptic skin cleansers commonly place denatured ethanol in the ~60–80% range (leave-on), which is the practical upper end for OTC products due to flammability, sensory irritation, and volatility constraints; rinse-off cleansers typically use lower levels than leave-on sanitizing/antiseptic formats.

Sea Salt

Sea salt (sodium chloride with trace minerals) is commonly used in cleansers and scrubs and can function as an abrasive or osmotic agent; at typical topical levels it is not a classic allergen but frequently causes stinging and dryness by increasing transepidermal water loss and irritating compromised barriers. Clinical experience and patch/usage data show higher intolerance in eczema, fissured skin, and post-procedure patients, where salt exposure predictably burns and can exacerbate inflammation. Because it can be moderately irritating in sensitive populations—especially when combined with surfactants or physical exfoliation—a moderate score with patch-test caution is warranted. Safety Notes: In commercial skincare, sea salt (typically sodium chloride with trace minerals) appears at very low levels (~0.05–0.5%) in leave-on toners/mists/creams mainly for skin-feel, ionic strength, and viscosity/texture tuning, and at low-to-moderate levels in cleansers and bath products (~0.5–10%). The highest consumer-available levels are found in rinse-off salt scrubs, polishing pastes, and “salt soap”/salt bar products where salt is a primary structurant and exfoliant, commonly 30–60% by weight. EU/FDA do not set a specific maximum for sodium chloride in cosmetics; practical upper limits are driven by product format (leave-on vs rinse-off), irritation potential, and processing/solubility constraints.

Sea Water

Sea Water is used mainly as a solvent/mineral source and can be present at meaningful levels in “marine” sprays and creams; its high salt content and mineral composition can be drying and stinging on compromised barriers (eczema, fissures, post-procedure skin). Clinically, hypertonic saline exposure is a known irritant on inflamed or broken skin and can exacerbate barrier disruption, so while many tolerate it on intact skin, reactive individuals can experience noticeable discomfort—warranting a mild irritancy score. Safety Notes: In mainstream skincare, Sea Water (often listed as Sea Water/Maris Aqua) is frequently used as a minor mineral/marketing component in emulsions, toners, and cleansers at ~0.1–5%. Many “marine” toners/mists and gel/serum bases use it as a significant portion of the water phase (~10–60%) to deliver salts/trace minerals while managing stability and sensory. At the high end, consumer-available sea-water sprays and seawater baths can be essentially undiluted seawater (near 100%), with practical limits driven by salinity, corrosion, and irritation potential; this applies mainly to leave-on mists/sprays and rinse-off/bath products.

Sea Whip Extract

Sea whip extract (typically a Pseudopterogorgia/sea whip coral extract) is used at low concentrations as an anti-inflammatory/soothing agent and is generally well-tolerated in leave-on products. However, as a marine-derived complex mixture (often containing multiple bioactive components and carried in solvents like glycols), it has a small but real risk of irritation or allergy in highly reactive or eczema-prone patients, so it cannot be scored as exceptionally gentle or inert. Safety Notes: In commercial skincare, Sea Whip Extract (often the gorgonian/“Pseudopterogorgia” extract marketed as an anti-irritant/soothing active) is frequently used at low levels (~0.05–0.5%) in mass-market lotions, cleansers, and after-sun products where it functions as a supporting soothing claim ingredient. Higher-strength consumer leave-on serums/ampoules and sensitive-skin concentrates commonly run ~1–3%, with the upper end around ~5% appearing in niche/high-claim products where the extract is a primary featured active and cost/odor/color constraints are managed. No specific global maximum is set for the extract itself (it’s generally managed under overall cosmetic safety), so the practical cap in OTC products is driven by supplier active assays, stability/compatibility, and sensory limits rather than regulation.

Sebacic Acid

Sebacic acid is a dicarboxylic acid most often used at low levels as a pH-adjusting/conditioning component or as part of exfoliating/anti-acne blends, and like other carboxylic acids it can sting on compromised skin depending on the final formula pH. While it is not typically as predictably irritating as strong leave-on exfoliating acids, clinical experience and patch-test patterns support occasional burning/erythema in highly reactive or eczematous users, especially when layered with other actives. For patient safety in sensitive populations, it warrants a mild irritancy rating rather than being treated as inert. Safety Notes: In commercial skincare, sebacic acid is most often seen in multi-acid/exfoliating or sebum-control formulas at low levels (~0.05–1%) as a supporting dicarboxylic acid alongside salicylic/glycolic acids, especially in leave-on toners/serums and some rinse-off cleansers. High-strength consumer products (typically leave-on peeling solutions or strong acne/exfoliation treatments marketed as multi-acid blends) have been observed up to about 10%, above which irritation and solubility/pH-management constraints tend to limit mainstream OTC use. No specific FDA/EU maximum concentration limit is commonly cited for sebacic acid itself, so practical formulation tolerability and product type (leave-on vs rinse-off) drive the market range.

Sericin

Sericin is a silk-derived protein used as a film-former and conditioning/humectant ingredient, typically included at low percentages in moisturizers and hair/skin conditioners. While generally well-tolerated and not an intrinsically irritating “active,” protein-based materials can provoke irritation or sensitization in a small subset of highly reactive or atopic patients, especially on compromised barrier skin. Given this nonzero allergy/irritation potential despite common cosmetic use, I rate it as gentle rather than exceptionally gentle. Safety Notes: In commercial skincare and haircare, sericin (silk protein) is most often used at very low levels (~0.01–0.1%) as a film-forming/conditioning additive in moisturizers, serums, shampoos, and conditioners, consistent with typical supplier use-level guidance and INCI placement low in the list. Higher-strength consumer products marketed as “silk protein/sericin” masks, ampoules, and repair treatments can reach ~1–5% active sericin (especially in leave-on masks/serums or intensive rinse-off treatments), with levels above this becoming uncommon due to viscosity/film feel, solubility/processing constraints, and cost; no specific global maximum is set, so the observed upper end is driven by formulation practicality rather than regulation.

Serine

MVP Approved - Serine is a naturally occurring amino acid used in skincare formulations primarily for its ability to help moisturize skin and support anti-aging benefits, while exhibiting very low irritation potential.

Sesamum Indicum Seed Extract

Sesamum indicum (sesame) seed extract is primarily a skin-conditioning botanical used at low concentrations, but sesame is a well-documented allergen and can trigger allergic contact dermatitis in a susceptible minority. While most users tolerate it, the sensitization risk in eczema-prone and highly reactive patients justifies a mild irritancy score, especially with leave-on, repeated exposure. Safety Notes: In mass-market and prestige skincare, Sesamum Indicum (Sesame) Seed Extract is most often used as a minor botanical/antioxidant claim ingredient in blends, with typical commercial inclusion levels at or below ~0.01–0.1%, and I have observed products listing it at trace levels consistent with ~0.001% in complex INCI decks. Higher-strength consumer-available products (especially facial oils, “botanical concentrate” serums, and some Korean/Japanese-style essence/ampoule products using dedicated sesame extract/glycerite) can reach the low single digits, with an observed upper end around ~5% before sensorial color/odor, stability, and cost typically become limiting; rinse-off uses generally sit toward the lower end due to brief contact time.

Sesamum Indicum Seed Oil

Sesamum Indicum (sesame) seed oil is primarily an emollient/occlusive lipid typically used at a few percent up to high levels in balms and oils, and it is not intrinsically caustic. However, sesame is a well-recognized allergen and sesame-derived ingredients can trigger allergic contact reactions in a susceptible minority (including eczema patients with impaired barriers), so sensitivity is plausible even when the base oil feels “gentle.” Given the real sensitization risk despite generally good tolerability, I rate it as mild rather than universally gentle for highly reactive skin. Safety Notes: In mass-market and prestige skincare, sesame seed oil is often used at very low levels (~0.05–0.5%) as a minor emollient/solvent within complex blends (e.g., lotions, creams, cleansers) where it appears mid-to-late in the INCI list. Dedicated face/body oils, oil cleansers, and bath oils commonly use it as a primary carrier at ~10–80%, and consumer-available single-ingredient “100% sesame oil” products (sold as skin/hair oil or multipurpose oil) represent the top end at 100%. There is no specific EU/FDA concentration cap for sesame seed oil in cosmetics, so the upper bound is primarily driven by product format and sensory/oxidative stability rather than regulation.

Sh-Oligopeptide-1

Sh-Oligopeptide-1 (often used to denote recombinant human EGF in a sh-oligopeptide naming system) is a skin-conditioning peptide typically used at very low concentrations and is not inherently acidic or surfactant-like, so primary irritancy is generally low in most users. However, as a bioactive signaling peptide delivered in leave-on products, there is a non-zero risk of stinging or reactivity in compromised barriers (eczema/post-procedure), and published irritation data are less robust than for inert humectants, warranting a cautious but still gentle score. Safety Notes: Sh-Oligopeptide-1 (commonly used as EGF) is typically supplied as a very dilute solution and is therefore used in commercial leave-on serums/creams at extremely low finished-product levels (often around 0.000001–0.0001%) to achieve ppb–ppm active dosing while maintaining stability and cost targets. High-strength consumer-available EGF serums marketed as “high concentration” commonly land in the ~0.001% range, with the upper end around ~0.01% in niche OTC products (above which cost and stability/handling constraints become significant); rinse-off use is uncommon and generally at the very low end due to limited contact time.

Sh-Oligopeptide-2

Sh-Oligopeptide-2 is a signal peptide used in very low concentrations in leave-on products (typically trace to <0.1%) to support skin conditioning/anti-aging claims. As a non-exfoliating, non-solvent, non-surfactant peptide, it has a low inherent irritation profile and is generally well-tolerated in patch testing and clinical use, though any bioengineered peptide can rarely trigger stinging or sensitization in highly reactive eczema-prone patients. Given the low use level but non-zero risk in compromised skin, it best fits a very gentle score rather than inert. Safety Notes: In commercial skincare, Sh-Oligopeptide-2 (a recombinant/“sh-” signaling peptide) is typically dosed at very low levels because it is supplied as a dilute solution/blend and is used for marketing/biological signaling rather than as a bulk active; many mass-market leave-on serums and creams effectively land around 0.00001–0.0001% active. Higher-strength consumer anti-aging serums and ampoules commonly reach ~0.001% active, with a practical observed ceiling around 0.01% in OTC leave-on products due to cost, stability, and diminishing returns; it is rarely used in rinse-off formats where contact time is short.

Sh-Pentapeptide-1

Sh-Pentapeptide-1 is a synthetic peptide used in anti-aging formulations at very low concentrations (typically 0.0001-0.001%), with clinical studies showing excellent tolerability and minimal irritation potential even in sensitive skin populations. Peptides of this molecular weight generally demonstrate low penetration and interaction with skin receptors, resulting in a favorable safety profile. While extremely rare sensitization reactions have been documented in literature, the ingredient's track record supports classification as very gentle and appropriate for daily use in most sensitive skin conditions. Safety Notes: Sh-Pentapeptide-1 (synthetic human Pentapeptide-1) is a highly potent cell-communicating peptide used in anti-aging formulations, typically found in leave-on serums and creams. The lowest commercial concentrations appear around 0.0001% in basic anti-aging moisturizers where it's a supporting ingredient, while specialized high-performance peptide serums can reach up to 0.01% as the active concentration. This peptide is extremely bioactive and expensive, so even at these seemingly low percentages, it represents significant formulation investment and efficacy at the cellular level.

Sh-Polypeptide-1

Sh-Polypeptide-1 is a recombinant human epidermal growth factor–type polypeptide used at very low levels (typically ppm-range) for skin-conditioning/anti-aging, and it is not pH-dependent or intrinsically exfoliating. In available cosmetic use, peptides like this show low rates of stinging/irritant patch-test reactions, with irritation more often driven by the formula’s preservatives/solvents rather than the peptide itself. Because it is a bioactive protein and compromised eczema skin can react unpredictably, I score it as very gentle rather than exceptionally gentle from a safety-first perspective. Safety Notes: Sh-Polypeptide-1 (commonly used as a recombinant “EGF”-type skin-conditioning peptide) is typically dosed extremely low in consumer leave-on serums and creams because activity is claimed at ppm-to-sub-ppm levels and higher loads raise cost and formulation challenges. At the low end, it appears in broad-market moisturizers/serums as part of multi-peptide blends where the finished-product level can be around 0.000001–0.0001%. At the high end, specialty “EGF” serums sold OTC can reach ~0.001–0.01% in the finished formula; rinse-off use exists but is uncommon and generally kept at the lower portion of the range due to short contact time.

Sh-Polypeptide-11

Sh-Polypeptide-11 is a synthetic/human-identical signaling peptide used in very low concentrations in leave-on products, and peptides as a class are generally well-tolerated with low rates of irritation in patch testing compared with acids, retinoids, or fragrance. The main safety concern is rare individual hypersensitivity to the peptide itself or residual impurities from manufacturing rather than intrinsic irritancy, so for highly reactive/eczema-prone skin it remains “very gentle” rather than inert. Safety Notes: Sh-Polypeptide-11 is a supplier-derived cosmetic peptide that is typically supplied as a diluted solution (often within a broader peptide/ferment blend) and is therefore used at very low active levels in commercial leave-on serums, eye products, and anti-aging creams, commonly landing in the ~0.00005–0.001% active range. Higher-strength consumer-available “peptide booster”/ampoule-style leave-on products and concentrated anti-wrinkle serums can push to about 0.01% active, above which cost, stability, and diminishing returns typically limit real-world OTC use. It is rarely a meaningful active in rinse-off products due to short contact time, so the observed market range is primarily based on leave-on formulations.

Sh-Polypeptide-9

Sh-Polypeptide-9 is a synthetic/human-identical signaling peptide used at very low levels in leave-on products (typically well under 0.1–1%), and peptides as a class show low irritation in standard patch-testing when properly formulated. The main risk is not inherent causticity but rare hypersensitivity or irritation from the overall formula (preservatives/solubilizers), so for patient-safety in highly reactive or eczema-prone skin I rate it as very gentle rather than exceptionally gentle. Safety Notes: Sh-Polypeptide-9 is a recombinant/cosmetic bio-peptide typically supplied as a dilute solution and used at very low levels in consumer leave-on serums and creams; at the low end it appears as a label-claim peptide at ~0.1–10 ppm active. Higher-strength OTC “peptide booster”/ampoule-type products and multi-peptide serums can reach ~0.01–0.05% active when the supplier solution is dosed aggressively, with higher levels uncommon due to cost, stability, and diminishing returns; it is rarely used meaningfully in rinse-off formats where deposition is limited.

Silanetriol

Silanetriol is a silicon-containing humectant/conditioning agent typically used at low concentrations in leave-on products and is not a pH-dependent exfoliating active. Available safety data and industry use history suggest low irritation potential with only occasional transient stinging reported in very reactive or barrier-compromised skin. Given limited independent clinical patch-test data compared with more common humectants, I score it as very gentle rather than exceptionally gentle to avoid underestimating risk in eczema-prone patients. Safety Notes: In commercial skincare, silanetriol is most often used as a trace-level silicon donor/humectant/conditioning active in leave-on serums and anti-aging moisturizers, where it commonly appears at very low levels (down to ~0.0005%) as part of broader complexes or to support label claims. High-strength consumer-available concentrates and “silicon/firming” ampoules can reach ~5% silanetriol, with higher levels limited by formulation stability, pH sensitivity, and potential for increased irritation/tack in leave-on products; rinse-off products generally use it at the low end due to short contact time. No specific FDA/EU maximum is established for silanetriol itself in cosmetics, so market practice and stability/skin tolerance are the primary practical constraints.

Silica

Silica (typically amorphous, used as an absorbent, anti-caking/texture agent in leave-on products and makeup) is generally well-tolerated at common use levels, with low rates of positive patch-test reactions. Irritation is uncommon but can occur in very reactive or barrier-compromised skin due to its oil-absorbing, mattifying effect increasing dryness and friction, so it is best rated as very gentle rather than inert for high-sensitivity populations. Safety Notes: In commercial skincare and makeup, silica (including amorphous silica, silica silylate, and microspheres) is used at very low levels (~0.05–0.5%) as a flow/anti-caking aid or minor sensory modifier in emulsions and cleansers, and more typically ~1–8% for oil-absorption, blurring, and slip in primers, sunscreens, and lotions. The highest consumer-available levels are found in anhydrous setting powders, blur powders, and some “silica microsphere” oil-control powders where silica can be a primary bulking/absorbing phase, reaching ~20–40% depending on the powder base (leave-on powders and primers trend higher than rinse-off products). Regulatory frameworks (EU/FDA) generally permit silica as used in cosmetics, with practical limits driven by aesthetics, dustiness/respiratory considerations for loose powders, and stability/viscosity in leave-on emulsions rather than a specific numeric maximum.

Silica Dimethyl Silylate

Silica Dimethyl Silylate is a treated silica used mainly as a thickener/anti-caking agent in anhydrous and silicone-based products, typically at low concentrations (about 0.1–5%), and it is generally considered non-reactive on skin. Clinical experience and patch-test data suggest low irritancy compared with many functional additives, but the particulate/absorbent nature can contribute to dryness or mild mechanical irritation in highly compromised barriers (e.g., active eczema), so it is not scored as fully inert. Safety Notes: Silica Dimethyl Silylate is used primarily as a hydrophobic thickener/gel former and suspending agent in anhydrous/oil-silicone systems; in many leave-on products (facial oils, primers, sunscreens, serums) it appears at low levels (~0.05–0.5%) to add slip, reduce greasiness, and help suspend pigments or UV filters. Typical functional use in emulsions and color cosmetics is commonly ~0.5–5% for structure and sensory modification, while high-strength consumer products like silicone putty primers, balm/gel textures, and some anhydrous foundations can reach ~10–15% to build a strong gel network and matte, blurring finish. It is far less common in rinse-off products and, when present, tends to stay at the low end because high levels can create excessive viscosity and poor rinsability.

Silica Silylate

Silica silylate is a hydrophobic fumed silica used as a thickener/texture agent and oil-absorbing powder, typically at low concentrations (about 0.1–5%) and is generally considered non-reactive on skin. Clinical experience and patch testing data suggest low irritation potential, but the particulate nature can be mildly drying or mechanically irritating in highly compromised barrier states (e.g., severe eczema or post-procedure skin), so it is not scored as completely inert for ultra-sensitive populations. Safety Notes: In commercial leave-on skincare and color cosmetics, silica silylate is often used at very low levels (~0.05–0.5%) as a rheology modifier/suspending aid (e.g., to stabilize oils, pigments, UV filters) and to boost slip/soft-focus in serums, sunscreens, and primers. Higher-load consumer products (notably oil-based primers, blurring powders, oil-control balms, and some anhydrous silicone/oil gels) can reach ~10–25% when it functions as a primary gellant/structurant and strong mattifying filler; these levels are observed in OTC retail products rather than prescription/professional-only items. There is no specific EU/FDA maximum for silica silylate in cosmetics, so the practical upper bound is set by sensory, clarity/whiteness, viscosity, and dispersion limits rather than regulation.

Silk

In skincare, “silk” typically refers to silk protein/sericin or hydrolyzed silk used at low concentrations as a film-forming conditioner, which is generally well tolerated and not intrinsically irritating like acids or solvents. However, as a protein-derived material it carries a non-zero risk of irritation or sensitization in highly reactive or eczema-prone patients (especially on compromised skin), and formulation impurities can increase reactivity. Given this small but real risk, it fits best as a gentle ingredient rather than inert. Safety Notes: In commercial skincare, silk is most often used as hydrolyzed silk/silk amino acids at very low levels (about 0.01–0.3%) as a marketing/skin-feel and conditioning additive in leave-on lotions, serums, and rinse-off cleansers. Higher-strength consumer-available products (e.g., specialty “silk protein” creams, masks, and concentrated hair/skin conditioning treatments) commonly reach ~1–3%, with a practical upper end around 5% due to solubility/viscosity, odor/color, and stability constraints rather than explicit regulatory limits.