Skincare Ingredients

Silk Powder

Silk powder (typically finely milled silk fibroin/sericin used at low percentages in cosmetics) is generally well-tolerated and functions mainly as an absorbent/texture enhancer rather than a reactive active. However, silk proteins can trigger irritation or allergic contact reactions in a minority of sensitized individuals, and particulate/powder forms can be mechanically irritating on compromised eczema skin. Given sensitive-skin safety priorities and the documented (though uncommon) protein sensitization risk, it fits best as a gentle but not "exceptionally gentle" ingredient. Safety Notes: In mass-market leave-on skincare and cosmetics, silk powder (often listed as Silk Powder, Silk, Serica Powder, or Hydrolyzed Silk in powder form) is commonly used as a slip/soft-focus and sensory modifier at very low levels, with commercial products observed starting around ~0.05–0.2%. Higher-loading consumer-available powders/primers, body powders, and mattifying/finishing products (and some “silk” masks or lotions marketed for a silky feel) can use multi-percent levels, with the upper end in real-world OTC products reaching roughly 10–20% in anhydrous loose/pressed powder-type formats. Rinse-off formats typically sit toward the lower end due to cost and limited deposition, while the highest levels are mainly seen in dry powder products where stability and viscosity limits are minimal.

Silt

Silt is a fine particulate mineral sediment used in masks/cleansers primarily for absorbency and mild physical exfoliation, typically at moderate-to-high percentages. While chemically inert, its particle load can mechanically irritate reactive or eczema-prone skin, especially with rubbing, compromised barriers, or concurrent use of other actives. Clinically, mineral particulates more often cause irritant (not allergic) reactions via friction and barrier disruption, so I score it as mild rather than inert for patient safety. Safety Notes: In commercial skincare, silt (fine mineral/earth particulate used for absorbency, exfoliation, and a “mud” sensorial claim) is sometimes included at very low levels (~0.1–1%) in cleansers, masks, and scrubs primarily for marketing/texture and mild oil-control. The highest consumer-available levels are seen in rinse-off mud/clay masks and body scrubs where the formula is largely mineral solids (often 20–60% total mineral phase, with silt as a major component), while true leave-on products typically stay much lower (generally <1–5%) due to grittiness, residue, and stability/settling constraints.

Silver

Topical silver (most often as metallic silver or silver salts in antimicrobial/wound and acne products, typically at low concentrations) is generally well-tolerated, but it is not inert because silver ions can be cytotoxic to keratinocytes at sufficient exposure and can irritate compromised skin. Clinical experience and patch-test literature suggest irritation is uncommon but possible, and allergic contact dermatitis has been reported to certain silver compounds (more than to elemental silver). Given sensitive/eczema-prone populations and leave-on use, I rate it as gentle with a small but real irritation/sensitization risk. Safety Notes: In consumer cosmetics, silver is most often present at trace antimicrobial/odor-control levels (e.g., colloidal/nano silver or silver salts in deodorants, lotions, masks, and cleansers), with real-world INCI usage commonly in the ~0.0001–0.05% range. The upper end is represented by high-strength OTC topical antimicrobial/barrier products marketed with “silver” (e.g., silver gels/creams using colloidal silver or silver-containing complexes), which can reach about 0.1–0.5% silver in leave-on formats; rinse-off products typically sit toward the lower end due to cost and deposition limits. Concentrations above this are uncommon for general-consumer cosmetics and more associated with medical devices or professional/prescription antimicrobial treatments rather than standard OTC skincare.

Silver Chloride

Silver chloride is used in topical products primarily for antimicrobial/odor-control purposes, typically at low concentrations, but silver salts can still provoke local irritation in reactive or compromised skin. Clinical and patch-test data suggest irritation is uncommon yet possible, and silver compounds also carry a non-trivial risk of contact dermatitis in sensitized individuals. Given eczema-prone populations and cumulative exposure in leave-on routines, I rate it as mild with occasional sensitivity potential. Safety Notes: In consumer skincare, silver chloride is typically used as a low-dose antimicrobial/deodorizing agent or as part of ‘silver’ preservative systems in leave-on creams, lotions, barrier products, and deodorant-style items, with marketed INCI-level use often in the ~0.0001–0.05% range. Higher-strength OTC consumer products (e.g., antimicrobial gels/creams, acne/blemish or foot/odor products, and some specialty hygiene leave-ons) can reach about 0.1–0.5% silver chloride, above which products are more commonly positioned as medical devices or drug-type antimicrobials rather than standard cosmetics. Rinse-off products generally sit toward the low end due to short contact time and cost/appearance constraints, while leave-on barrier/odor-control products more often approach the upper end.

Silybum Marianum Extract

Silybum Marianum (milk thistle) extract is primarily used as an antioxidant/soothing botanical, typically at low concentrations (often <1–2%) in leave-on products, and is generally well tolerated in clinical and consumer use. However, as a plant extract it contains multiple phytochemicals and can trigger irritation or allergic contact reactions in a minority of sensitized or highly reactive patients (including those with eczema or botanical allergies), so it cannot be scored as “very gentle” for all compromised skin. Safety Notes: In mass-market leave-on skincare (creams/serums/toners), Silybum marianum (milk thistle) extract is commonly included at very low supportive levels (~0.01–0.1%) as part of antioxidant/soothing blends, consistent with typical botanical extract dosing and supplier recommended use levels. Higher-strength consumer products (especially “antioxidant,” “detox,” or post-procedure-calming serums) can reach ~1–5% when the ingredient is a primary featured extract or supplied as a concentrated glycerin/butylene glycol extract; above this is uncommon due to solubility/appearance/odor and increasing formula instability or tack. Rinse-off products typically sit toward the lower end because of short contact time, while the upper end is primarily observed in leave-on formulations.

Silybum Marianum Fruit Extract

Silybum Marianum (milk thistle) fruit extract is primarily an antioxidant/soothing botanical used at low concentrations (commonly well under 1%) and is generally well tolerated in leave-on products. However, as a complex plant extract it can still trigger irritation or allergic contact dermatitis in a small subset of highly reactive or eczema-prone patients, especially when formulations contain multiple botanicals. Given that nonzero sensitization potential exists but routine irritancy is uncommon, a gentle score is appropriate. Safety Notes: In commercial skincare, Silybum Marianum (milk thistle) fruit extract is most often used as a minor botanical antioxidant/soothing support ingredient at very low levels (around 0.0005–0.1%) in leave-on creams/serums and rinse-off cleansers, reflecting typical supplier-use levels and INCI list placement. Higher-strength consumer-available products (botanical-focused serums, ampoules, masks) can reach ~1–5% extract, especially when the extract is the headline active or part of a standardized botanical complex; above this is uncommon due to solubility, sensory, and stability constraints rather than regulation. No specific FDA/EU cosmetic concentration limit is set for this extract, so the practical upper end is driven by formulation feasibility and market practice.

Silybum Marianum Seed Oil

Silybum Marianum (milk thistle) seed oil is primarily an emollient lipid used at a few percent to higher levels in moisturizers, and as a non-volatile oil it is generally well tolerated with low intrinsic sting potential. However, like other botanical seed oils it can contain minor unsaponifiables/trace proteins and oxidation byproducts that occasionally trigger irritant or allergic contact dermatitis in highly reactive or eczema-prone patients, especially in compromised barriers. Given this low-but-real risk in sensitive populations, it fits best as a gentle ingredient rather than exceptionally gentle. Safety Notes: In commercial skincare, Silybum Marianum (milk thistle) seed oil is often used as a minor emollient/marketing botanical in leave-on creams, serums, and cleansers at very low levels (~0.01–0.1%), commonly within a broader plant-oil blend. Mid-range usage (~0.5–5%) appears in facial oils, barrier creams, and antioxidant-focused leave-on products where it contributes slip and unsaponifiables, while the top end includes consumer-available single-ingredient carrier oils sold as “100% milk thistle seed oil” or predominantly milk-thistle facial oils approaching 100%. No specific EU/FDA cosmetic maximum is set for this fixed oil; practical limits are driven by odor/feel, oxidation control, and compatibility in emulsions (leave-on typically higher than rinse-off).

Simethicone

Simethicone (a silicone-based skin protectant/occlusive and slip agent) is typically used at low-to-moderate levels in creams, lotions, and barrier products and is widely considered non-sensitizing with very low irritancy in patch testing and clinical use. True irritation or allergy is uncommon and usually related to the overall formula rather than simethicone itself, but in severely compromised skin any film-former can rarely contribute to occlusive discomfort or trapping of other irritants. For patient safety in highly reactive/eczema populations, it fits best as exceptionally gentle rather than completely inert. Safety Notes: In consumer skincare, simethicone is most often used at low levels (~0.1–1%) as a slip agent, anti-foam/processing aid, and skin protectant/emollient component in moisturizers, primers, sunscreens, and cleansers (rinse-off typically at the low end). Higher-strength OTC products marketed as barrier/skin-protectant creams, chafing/friction balms, and some “silicone-rich” smoothing primers commonly reach ~2–5% total simethicone for a more occlusive, blurring feel. This range reflects observed commercial usage; higher levels are limited by sensory, stability, and regulatory/product-positioning considerations rather than a strict cosmetic maximum in major markets.

Simmondsia Chinensis Butter

Simmondsia Chinensis Butter (jojoba-derived butter) functions as an emollient/occlusive and is typically used at a few percent up to higher levels in balms; it is generally well tolerated and supportive for barrier-compromised skin. Clinical experience and patch-testing data for jojoba derivatives suggest low irritancy, but rare allergic/contact dermatitis can occur—sometimes due to oxidation products or formulation impurities—so it is not fully “inert.” For high-sensitivity populations (eczema, impaired barrier), this fits best as very gentle with a small but nonzero risk. Safety Notes: In commercial skincare, Simmondsia Chinensis (Jojoba) Butter is often used at low levels (~0.1–1%) as an emollient/structuring lipid in lotions, creams, cleansers, and lip products where it contributes slip without strongly impacting rheology or cost. Mid-to-high levels (5–30%) are common in richer body butters, balms, and barrier creams as a primary lipid phase component. The upper end includes consumer-available “100% jojoba butter” or anhydrous balm-style products marketed as single-ingredient butters; rinse-off products typically stay at the low end due to deposition/economics and the need for surfactant compatibility, while leave-on anhydrous formats can reach the maximum.

Simmondsia Chinensis Seed Oil

Simmondsia Chinensis (jojoba) seed oil is primarily an emollient/wax ester used at moderate-to-high levels in moisturizers and is generally well tolerated, including in eczema-prone skin, with low rates of irritant reactions in clinical use. However, as a botanical lipid it is not completely inert—rare irritation or allergy can occur (especially with oxidized/impure oils or in highly compromised barriers)—so I do not score it as exceptionally gentle/inert. For patient safety in very reactive populations, a small but real irritation potential warrants a very gentle (0.2) score. Safety Notes: In commercial skincare, jojoba oil is frequently used at very low levels (~0.1–1%) as an emollient/skin-feel modifier in lotions, creams, cleansers, and shampoos, and at moderate levels (2–20%) in facial oils, body oils, balms, and barrier creams. The top of the observed consumer market includes 100% pure jojoba oil sold as a standalone leave-on oil, which is widely available OTC; rinse-off products typically sit at the low end due to cost, foaming/performance constraints, and wash-off.

Sisymbrium Irio Seed Oil

Sisymbrium irio (London rocket) seed oil is primarily an emollient lipid used at low percentages to improve slip and barrier feel, but it comes from a Brassicaceae seed source that can contain bioactive minor components (e.g., glucosinolate breakdown products) that are not as well-characterized for tolerability as more common seed oils. Clinical irritation/sensitization data are limited, so for highly reactive or eczematous patients I cannot classify it as “very gentle” despite typical low use levels. Given the uncertainty and the potential for idiosyncratic reactions in compromised skin, a mild irritancy score best reflects patient-safety-first risk management. Safety Notes: In commercial skincare, Sisymbrium Irio Seed Oil is most often used as a minor emollient/conditioning specialty oil in leave-on formulas (serums, creams, facial oils) at trace-to-low levels (~0.01–1%) to support sensory feel and marketing claims, and occasionally a few percent in anhydrous blends. At the high end, consumer-available single-ingredient or near-neat botanical oils can be marketed as 100% seed oil (or functionally neat), making 100% the observed maximum for OTC leave-on oils; rinse-off usage is typically at the lower end due to cost and wash-off inefficiency.

Skeletonema Costatum Extract

Skeletonema Costatum Extract is a marine microalgae (diatom) extract typically used at low concentrations for antioxidant/soothing or conditioning claims, but it is a complex botanical mixture rather than a single inert molecule. While broad clinical irritation data are limited, algae extracts can trigger stinging or dermatitis in reactive/eczema-prone users due to variable proteins/polysaccharides and potential trace contaminants from cultivation, making occasional sensitivity plausible. Given the uncertainty and patient-safety priority, I rate it as mild irritancy rather than assuming it is universally gentle. Safety Notes: In commercial skincare, Skeletonema costatum (a marine microalgae/diatom) extract is most often used as a low-dose “active” within blends, with many leave-on serums/creams listing it at trace-to-low levels around 0.001–0.05% to support antioxidant/soothing claims while maintaining color/odor and stability. Higher-strength consumer products (typically leave-on ampoules, concentrates, or “microalgae” booster serums) can reach ~0.5–2.0% when the extract is supplied as a usable solids content active; above this is uncommon in OTC due to cost, sensory impact, and formulation stability constraints. Rinse-off products generally sit toward the low end because of short contact time and foam/surfactant compatibility.

Snail Secretion Filtrate

Snail secretion filtrate is primarily a humectant/skin-conditioning ingredient used at a few percent up to higher levels in “snail” serums, and it is generally well-tolerated but not inert. Patch-test and consumer reports show occasional irritation or allergic-type reactions (itching, stinging, flares) in reactive or eczematous patients, likely due to its complex protein/glycoprotein composition and potential trace impurities from processing. Given the non-trivial risk in compromised barriers and the need to err on patient safety, I score it as mild rather than gentle. Safety Notes: In commercial skincare, snail secretion filtrate appears at very low levels (~0.1–1%) in multi-ingredient creams/cleansers and some rinse-off products where it functions mainly as a minor humectant/marketing active. Mid-range leave-on essences/serums commonly use ~10–40%, while multiple widely sold consumer essences/ampoules are marketed as very high snail content (typically ~80–96% and up to ~97%), which represents the upper end observed for OTC leave-on products rather than a regulatory maximum.

Sodium Acetate

Sodium acetate is primarily a buffering/pH-adjusting salt used at low concentrations (typically well under a few percent) to stabilize formulas, and it is generally well tolerated in clinical and consumer use. While not a classic irritant, any electrolyte/buffer can sting on compromised skin (eczema flares, post-procedure) or if it contributes to a higher local pH, so I do not score it as inert. Overall, its irritation potential at typical use levels is low, making it very gentle for most sensitive users. Safety Notes: Sodium acetate is most often used as a minor pH adjuster/buffer or ionic-strength modifier in toners, cleansers, shampoos, and some leave-on serums/creams, where it can appear at trace-to-low levels (around 0.01–0.1%) alongside acetic acid/acetates. Higher levels are seen in consumer-available buffered systems and some mask/peel-type or deodorant/antiperspirant-style formulations where salt/buffer load is intentionally increased, with practical OTC maxima typically around 3–5% before sensorial, solubility, and irritation/pH constraints become limiting. It is not specifically restricted by EU/FDA as a cosmetic ingredient, so the upper end is driven mainly by formulation performance and tolerability rather than a hard regulatory cap.

Sodium acetylated hyaluronate

Sodium acetylated hyaluronate is a modified hyaluronic acid humectant used at low concentrations (typically well under 1%) to improve hydration and barrier feel; hyaluronate polymers are generally well-tolerated in clinical use and patch testing with very low irritancy rates. Rare stinging or transient redness can occur in highly reactive or severely compromised skin (often influenced by the full formula/pH rather than the polymer itself), so it is not scored as completely inert but remains very gentle for most sensitive users. Safety Notes: In commercial products, sodium acetylated hyaluronate is often used as a premium hyaluronic-acid derivative at very low levels (around 0.0005–0.01%) in multi-HA complexes, emulsions, and toners/cleansers where it functions mainly as a film-forming humectant and label claim ingredient. Leave-on serums and masks marketed for long-lasting hydration commonly sit around 0.01–0.1%, while a small number of high-strength consumer-available “concentrated” HA serums/gels and sheet mask essences push this specific derivative up to ~0.2–0.3% for enhanced substantivity; higher levels are uncommon due to cost, viscosity/tack, and formulation aesthetics rather than regulatory limits.

Sodium Acrylates Copolymer

Sodium Acrylates Copolymer is a high–molecular weight synthetic film-former/thickener used at low concentrations (typically well under a few percent) and is generally not skin-penetrating, with patch-test data and broad cosmetic use suggesting very low irritancy. In most formulas it functions as an inert texture/viscosity agent rather than a reactive active, so clinically significant irritation is uncommon. Rare stinging or dermatitis can still occur in highly compromised barriers or from the overall formula matrix, so I score it as exceptionally gentle rather than completely inert. Safety Notes: In commercial skincare, sodium acrylates copolymer is commonly used as a rheology modifier/film former at very low levels (~0.05–0.3%) in lotions, serums, and sunscreens (leave-on) to build viscosity, stabilize emulsions, and improve slip. Higher levels (1–5%) are seen in thicker gel-creams, peel-off/film-forming masks, and some makeup-skincare hybrids to create structure and a continuous film; the upper end (~8–10%) occurs in consumer-available high-hold styling/film gels or specialized mask/primer-type products where the polymer is the primary structurant rather than a minor stabilizer. Rinse-off cleansers typically sit toward the low-to-mid end because excessive levels can feel tacky and can be harder to rinse clean.

Sodium Acrylates Crosspolymer-2

Sodium Acrylates Crosspolymer-2 is a synthetic polymer thickener/film former used at low levels (typically well under 1–2%) to stabilize gels and improve texture rather than act as a bioactive. In clinical use and patch testing, crosslinked acrylate polymers are generally considered very low-irritant and non-sensitizing, with reactions being uncommon and usually related to damaged barriers or impurities rather than the polymer itself. Given the rare but possible stinging in severely compromised skin, I score it as exceptionally gentle rather than fully inert. Safety Notes: In commercial leave-on emulsions, gels, and sunscreens, Sodium Acrylates Crosspolymer-2 is commonly used as a rheology modifier/suspending polymer at very low levels, with market-observed use down to ~0.05% when paired with other thickeners. Typical mainstream products fall around ~0.1–0.8%, while high-viscosity consumer styling gels, acne gels, and heavy-duty suspending/gel textures can push toward ~1.5–2.5% to build yield value and stabilize particulates. It is used in both leave-on and rinse-off formats, but the highest levels are more often seen in thick leave-on gels where maximum structure and suspension are needed.

Sodium Anisate

MVP Approved - Sodium Anisate is a preservative used in skincare formulations for its antimicrobial activity and is generally recognized as a gentle, low‐irritancy ingredient.

Sodium Ascorbate

Sodium ascorbate is a vitamin C salt used as an antioxidant/skin-conditioning agent, typically at low-to-moderate concentrations (often a few percent) and generally better tolerated than acidic L-ascorbic acid because it is less pH-dependent and less stinging at use levels. However, in very reactive or eczema-prone skin it can still provoke mild irritation (especially at higher concentrations or when layered with other actives), so it is best classified as gentle rather than exceptionally gentle. Safety Notes: In commercial skincare, sodium ascorbate is used at very low levels (~0.05–0.2%) primarily as an antioxidant/label claim support ingredient in emulsions and rinse-off cleansers where it contributes minimal vitamin C delivery. Most leave-on antioxidant serums/lotions that use sodium ascorbate (instead of ascorbic acid) fall around ~1–5% due to solubility, sensory, and stability constraints. High-strength consumer-available water-based vitamin C serums and powdered/DIY “mix-in” boosters reach about 10–20% sodium ascorbate; above this, products tend to suffer from stickiness, crystallization, and pH/compatibility issues, and higher strengths are uncommon in true OTC finished formulas.

Sodium Ascorbyl Phosphate

MVP Approved - Sodium Ascorbyl Phosphate is a stable, water‐soluble vitamin C derivative noted for its antioxidant, brightening, anti‐aging, and acne‐fighting properties. It is generally well tolerated with minimal irritation, making it suitable for sensitive and acne‐prone skin.

Sodium Benzoate

MVP Approved - Sodium Benzoate is a synthetic preservative commonly used in cosmetic formulations to prevent microbial growth, and it is generally well tolerated at recommended concentrations.

Sodium Benzotriazolyl Butylphenol Sulfonate

Sodium Benzotriazolyl Butylphenol Sulfonate is a water-soluble UV filter/stabilizer used in low percentages (often ~0.5–5%) to improve photostability; it is a large, highly sulfonated molecule with limited skin penetration, which generally supports good tolerability. Available patch-test and post-market data suggest a low but non-zero risk of irritation or rare sensitization, particularly in compromised barriers (e.g., eczema) or when combined with multiple UV filters/solubilizers that can cumulatively irritate. Given the stakes for highly reactive patients, I rate it as gentle but not inert. Safety Notes: Sodium Benzotriazolyl Butylphenol Sulfonate is a water-soluble UV absorber/photostabilizer (often supplied as an aqueous solution) used at very low levels (~0.05–0.3%) in daily moisturizers/serums and many sunscreens primarily to protect formula color/fragrance and improve UV filter photostability. In high-UV, long-wear leave-on products—especially tinted/mineral-hybrid sunscreens and anti-pollution/day-shield products—commercially observed use can reach ~1–3% active to boost photostability and reduce photo-degradation of dyes and actives; rinse-off products tend to sit at the low end due to limited benefit and cost. There is no specific EU/FDA maximum limit widely codified for this stabilizer in cosmetics, so market practice and solubility/tolerance typically set the upper bound in consumer OTC products.

Sodium Bisulfite

Sodium bisulfite is a reducing agent/antioxidant preservative used at low levels (often ~0.1–1%) but is a well-documented irritant and can provoke adverse reactions in sensitive individuals, especially those with eczema or sulfite sensitivity. It can cause stinging, erythema, and eczematous reactions on compromised skin, and its sensitization/trigger potential warrants careful introduction and patch testing rather than assuming it is “gentle.” Safety Notes: In commercial cosmetics, sodium bisulfite is most often used at very low levels (around 0.001–0.05%) as an antioxidant/reducing agent to protect oxidation-prone ingredients (e.g., certain dyes, botanical extracts, or to stabilize some solutions), with the lowest levels commonly seen in leave-on serums/creams where odor/irritation and sulfite sensitivity are concerns. Higher levels are mainly observed in rinse-off products—especially hair color/bleach-related and some cleansing systems—where it can function as an oxygen scavenger/reductant, with consumer-available products reaching about 0.5–1.0%. While not universally capped by a single global maximum in the same way as some preservatives, practical sensory/compatibility limits and sulfite-allergy labeling considerations typically constrain leave-on use to the low end of this range.

Sodium Borate

Sodium borate (borax) is an alkaline buffering/cleaning salt; in leave-on or rinse-off products its higher pH and salt nature can disrupt the stratum corneum and sting compromised skin, especially in eczema. Patch-test and occupational data show it can be irritating to skin and mucosa at relevant exposures, even if it is not a common true allergen. Given sensitive-skin populations and cumulative routine use, I rate it as a moderate irritant where irritation is plausible and patch testing is prudent. Safety Notes: In modern OTC cosmetics, sodium borate (borax) is most often present at very low levels (around 0.01–0.3%) as a pH adjuster/buffer or formulation aid in rinse-off products (soaps, cleansers) and some leave-on items where permitted. Higher concentrations exist in consumer-available niche products that function more like topical antiseptic/astringent or powder-to-solution preparations (and some legacy formulations), where borate salts can reach low single-digit percentages; above ~5% is uncommon in mainstream skincare due to sensitization/irritation risk and tighter boron-related regulatory scrutiny (notably in the EU, which restricts/limits boron compound use depending on product type and exposure).

Sodium C14-16 Olefin Sulfonate

Sodium C14-16 Olefin Sulfonate is a strong anionic surfactant/cleansing agent commonly used at functional levels in shampoos and foaming cleansers, where it can significantly strip barrier lipids and increase transepidermal water loss. Clinical and patch-test experience shows a relatively high potential for irritation (stinging, erythema, dryness), especially in eczema-prone or compromised skin, and cumulative exposure in multi-step routines increases risk. Because it is frequently perceived as a “sulfate-free” alternative but can be comparably harsh, I score it as high irritancy for sensitive populations. Safety Notes: In consumer products, Sodium C14-16 Olefin Sulfonate is primarily used in rinse-off cleansing systems; at the low end it appears around 0.5–2% in mild facial cleansers/body washes where it is blended with amphoterics/nonionics to reduce irritation. Mainstream shampoos and facial/body cleansers commonly use ~3–12% (as active), while high-foam clarifying shampoos, deep-clean body washes, and some acne/oily-skin cleansers marketed to consumers can reach ~15–25% total surfactant active from this material. It is rarely used in leave-on products due to irritation potential, so the observed high end is effectively confined to rinse-off formulas.

Sodium Caproyl Methyltaurate

Sodium Caproyl Methyltaurate is a mild anionic surfactant used mainly in cleansers (often a few percent up to ~10%+) to provide foaming/cleansing with lower irritation than harsher sulfates. Clinical and practical patch/usage experience generally show good tolerability, but as a true cleansing surfactant it can still cause stinging or barrier dryness in eczema-prone or over-cleansed patients, especially in multi-surfactant formulas or frequent use. For patient safety in severe sensitivity, I score it as gentle but not “very gentle,” reflecting its low yet non-zero irritation potential. Safety Notes: Sodium caproyl methyltaurate is primarily used as a mild anionic surfactant/co-surfactant, so it appears at very low levels (~0.1–1%) in leave-on emulsions and micellar/cleansing waters for mildness or foam support, while most rinse-off facial/body cleansers and shampoos commonly use it in the ~2–10% range. High-foaming, sulfate-free consumer cleansers and shampoo bars/liquid concentrates can reach ~15–20% active surfactant levels where it serves as a principal surfactant in the system. No specific EU/FDA concentration limit applies; the upper end is practically constrained by irritation potential, viscosity/clarity targets, and overall surfactant active load rather than regulation.

Sodium Carbomer

Sodium carbomer is a crosslinked polyacrylate gelling/thickening polymer typically used at low concentrations (~0.1–1%) to stabilize texture and suspend actives, and it is not intrinsically reactive or exfoliating. Clinical and patch-testing experience generally shows very low irritation potential, with occasional stinging or dryness more often attributable to the overall formula (pH, alcohols, surfactants) rather than the polymer itself. For highly compromised or post-procedure skin, I still assign a small nonzero risk due to rare individual sensitivity and the possibility of barrier discomfort in already-inflamed patients. Safety Notes: In commercial skincare, sodium carbomer (neutralized carbomer) is typically used as a rheology modifier/gel former at very low levels (~0.05–0.30%) in serums, lotions, and cleansers where it mainly provides viscosity and suspension. Higher-viscosity consumer gel products (e.g., clear facial gels, hydrogel-type moisturizers, some aftersun/aloe gels) commonly run ~0.5–1.0%, and the highest OTC ‘gel base’/single-phase thick gels sold to consumers can reach about 2.0% to achieve very firm, high-yield stress textures (above this is uncommon due to tack/drag and processing limits). Leave-on and rinse-off products overlap strongly, with rinse-off often sitting at the low end because less structure is needed at use.

Sodium Carbonate

Sodium carbonate (washing soda) is a strongly alkaline pH adjuster/buffer; even at low leave-on levels it can raise product pH enough to disrupt the stratum corneum, increasing stinging and barrier damage in eczema-prone or compromised skin. In rinse-off products it’s often used at higher effective alkalinity, where clinical experience and patch/occupational data show notable irritant potential, especially with repeated exposure. Given its caustic alkalinity and high likelihood of barrier disruption in sensitive users, it warrants a high irritancy score. Safety Notes: In consumer skincare/cosmetic products, sodium carbonate is most often used at very low levels (~0.01–0.5%) as a pH adjuster/alkalizing buffer in rinse-off cleansers, soaps, and some bath products, with occasional use around ~1% in strongly alkaline cleansing systems. The highest consumer-available concentrations are found in highly alkaline cleansing powders/pastes and specialty exfoliating/cleansing products positioned as “deep-clean” or “soap-based,” where sodium carbonate can function as a primary builder/alkalinity source and reach roughly 10–20% in anhydrous or low-water formulas. It is generally unsuitable for leave-on skincare at meaningful levels due to high alkalinity/irritation risk, so high-end concentrations are overwhelmingly rinse-off.

Sodium Carboxymethyl Beta-Glucan

Sodium carboxymethyl beta-glucan is a water-soluble, film-forming polysaccharide derivative used mainly as a soothing/humectant and barrier-support ingredient, typically at low concentrations (about 0.1–1%). Available patch/usage data for beta-glucans and their derivatives generally shows very low irritation and good tolerability even in compromised skin, with reactions being uncommon and usually idiosyncratic rather than concentration-driven. I score it as very gentle (0.2) rather than exceptionally gentle/inert because polymer modifications and impurities can rarely trigger stinging or contact reactions in highly reactive eczema-prone patients. Safety Notes: In commercial skincare, sodium carboxymethyl beta-glucan (a water-soluble, modified beta-glucan used for soothing/barrier support) is commonly used at very low levels (~0.01–0.1%) in serums, toners, and moisturizers where it functions as an anti-irritant/film-former alongside other humectants. Mainstream leave-on products more typically sit around ~0.1–0.5%, while high-strength consumer OTC “repair” or post-procedure calming serums/ampoules and some mask essences can reach ~1–2% before viscosity/film feel and cost become limiting; rinse-off cleansers are usually at the low end due to short contact time.

Sodium Carboxymethyl Starch

Sodium carboxymethyl starch is a modified polysaccharide used primarily as a thickener/absorbent in leave-on and rinse-off products, typically at low single-digit percentages. Available safety and patch-test experience with similar carbohydrate polymers suggests very low intrinsic irritation and minimal sensitization risk, but rare reactivity can occur in highly compromised eczema skin due to barrier disruption and product matrix effects. Given it is not truly inert yet is generally well-tolerated, it fits a very gentle (0.2) rating for most sensitive-skin use. Safety Notes: In commercial skincare, sodium carboxymethyl starch is most often used as a secondary thickener/texture modifier and suspension aid at low levels (~0.05–0.5%) in serums, lotions, and cleansers, where it fine-tunes slip and stabilizes dispersed phases. Higher-use levels (~2–8%) are observed in consumer-available high-solids gel-creams, matte/blur primers, and some powder-to-cream or styling/setting-type skincare hybrids where it functions as a primary rheology builder and oil-absorbing structurant. It is used in both leave-on and rinse-off products, with the highest levels more common in leave-on texture-focused formats; no specific EU/FDA cosmetic concentration cap is generally applied beyond safety substantiation and performance/stability constraints.