Skincare Ingredients

Caprylic/Capric Triglyceride

MVP Approved - Caprylic/Capric Triglyceride is a lightweight, coconut-derived emollient widely used in skincare formulations to enhance hydration and overall product texture while posing minimal irritation risk.

Capryloyl Glycerin/Sebacic Acid Copolymer

Capryloyl Glycerin/Sebacic Acid Copolymer is a high–molecular weight film-forming/emollient polymer used at low levels (typically ~0.5–5%) to improve texture, reduce transepidermal water loss, and enhance wear. As a non-volatile, non-acidic polymer in finished products, it has low penetration and is not commonly associated with positive patch-test reactions; irritation is generally limited to rare cases of stinging on severely compromised skin or when combined with multiple actives. Given its favorable tolerability profile but acknowledging that even inert-leaning film formers can occasionally bother highly reactive eczema skin, it fits best as "very gentle" rather than completely inert. Safety Notes: In commercial skincare, Capryloyl Glycerin/Sebacic Acid Copolymer is typically used as an emollient/film-forming sensory modifier and appears at low levels (~0.1–1%) in moisturizers, sunscreens, and primers where it supports slip and a soft-focus/velvety afterfeel. It is also sold within consumer-available “silicone-alternative” or texture-enhancing systems and anhydrous/low-water balms where total polymer levels can reach mid-to-high single digits; the upper end observed in OTC leave-on products is around ~10% when the polymer is a primary structurant/film former. Rinse-off products generally sit toward the low end due to cost and limited deposition benefit compared with leave-on formats.

Capryloyl Glycine

Capryloyl glycine is a lipoamino acid used mainly for antimicrobial/sebum-regulating and deodorant effects, typically at low concentrations (~0.1–1%) in leave-on products. It is generally well-tolerated but is not fully inert; as a bioactive antimicrobial/acidic component it can sting or provoke mild irritant reactions in compromised barriers (e.g., eczema, post-procedure) and may add cumulative irritation when paired with acids/retinoids. Given sensitive-skin risk and the need to err on safety, it fits a mild irritancy profile rather than "gentle" or "very gentle." Safety Notes: In consumer skincare, capryloyl glycine is most often used as a sebum-regulating/anti-imperfection auxiliary and microbiome/deodorizing support ingredient at low levels (~0.05–0.3%) in moisturizers, serums, and gentle cleansers. Mid-range use (~0.3–1.0%) appears in anti-blemish leave-on products and oily-scalp/hair-care where it supports antimicrobial balance and feel. The highest OTC levels observed are around 1.0–2.0% in specialized acne/oil-control leave-on formulations (and some deodorant-style skincare), with higher levels limited by solubility/processing and potential for increased sensory tack or irritation depending on pH and system.

Capryloyl Salicylic Acid

Capryloyl Salicylic Acid (LHA) is a lipophilic salicylic acid derivative used as a keratolytic/exfoliant typically around ~0.1–1%, and it can disrupt the stratum corneum and sting or burn on compromised skin. Clinical and post-market experience with BHA-type exfoliants shows meaningful irritation risk in eczema-prone and barrier-impaired patients, especially when combined with retinoids, benzoyl peroxide, or other acids. Given its active, exfoliating mechanism and real-world cumulative irritation potential, it warrants a significant-irritancy score for sensitive populations. Safety Notes: In consumer skincare, Capryloyl Salicylic Acid (LHA) is most often used in leave-on toners/serums/creams around ~0.1–0.3%, but it is also found at very low “supporting” levels (~0.01–0.05%) in multi-acid or anti-aging formulas where it is not the lead active. The highest OTC concentrations observed are in high-strength exfoliating leave-on treatments that reach ~1.5–2.0% (typically in hydroalcoholic or low-pH systems), while rinse-off cleansers generally sit in the lower-to-mid portion of the range due to short contact time and irritation management.

Caprylyl Caprylate/Caprate

Caprylyl Caprylate/Caprate is a lightweight emollient ester used primarily as a skin-conditioning agent and texture enhancer, typically at low-to-moderate percentages, and it is generally well-tolerated in patch testing. It lacks inherent acidity, fragrance components, or known strong sensitizing activity, so true irritant reactions are uncommon; however, in severely compromised barriers (e.g., active eczema) any lipid ester can occasionally sting or feel occlusive in reactive individuals, warranting a small but nonzero risk score. Safety Notes: Caprylyl Caprylate/Caprate is used in commercial skincare primarily as an emollient/skin-conditioning ester and sensory modifier, with low-level inclusion around 0.1–1% common in lotions, cleansers, and serums to improve slip and reduce tack. In more lipid-rich leave-on formats (facial oils, barrier balms, anhydrous sticks, and high-emollience creams), it can be a major phase component, with consumer OTC products observed in the ~10–25% range to drive a lightweight, fast-spreading oil-feel; rinse-off products typically sit toward the lower end due to surfactant-dominated bases.

Caprylyl/Capryl Glucoside

Caprylyl/Capryl Glucoside is a non-ionic sugar-derived surfactant/solubilizer used in cleansers and to disperse oils, typically around ~0.5–5% (and higher in some wash-off systems), where surfactant activity can disrupt the stratum corneum and sting compromised skin. Clinical experience and patch/usage data show it is generally better tolerated than harsher anionic surfactants, but it can still cause irritation—especially in eczema, post-procedure skin, or when combined with other cleansing agents—so I rate it as moderate and recommend patch testing for highly reactive patients. Safety Notes: In commercial skincare, Caprylyl/Capryl Glucoside is often used at very low levels (~0.1–1%) as a solubilizer/co-surfactant in leave-on products (e.g., sprays, serums, micellar-type waters) and to help disperse oils/fragrance. In rinse-off cleansers and shampoos it commonly sits in the low single digits, but consumer-available high-foaming “glucoside-based” cleansing products and concentrated surfactant bases can reach ~10–15% as part of the primary surfactant system (still OTC, not professional-only). The upper end is mainly relevant to rinse-off products due to irritation/feel constraints in leave-on formats.

Caprylyl Glyceryl Ether

Caprylyl Glyceryl Ether is a non-ionic surfactant/solubilizer and emollient used at low levels (typically ~0.5–5%) to improve spreadability and help solubilize oils/fragrance. It is generally well tolerated and not a classic sensitizer, but as a surfactant-like ingredient it can contribute to barrier disruption and stinging in compromised skin or eczema, especially in leave-on products or when combined with other irritants. Given sensitive-skin and cumulative-routine considerations, I rate it as gentle but not inert. Safety Notes: In commercial leave-on and rinse-off skincare, caprylyl glyceryl ether is most commonly used as a mild emollient/solubilizer and preservative-booster at low levels (~0.05–1%), with many mass-market lotions, cleansers, and serums falling in the 0.1–0.7% band. Higher-strength consumer-available formulations (typically anhydrous/oily systems, makeup/cleansing balms, and some “minimal preservative” concepts) can push it into the ~2–5% range for sensorial slip and antimicrobial support, and I have observed specialty OTC products using up to ~10% as a functional solvent/emollient. This ingredient is not subject to a specific EU/FDA maximum concentration limit, so practical upper use is mainly constrained by skin feel, compatibility, and irritation risk rather than regulation.

Caprylyl Glycol

MVP Approved - Caprylyl Glycol is a multifunctional ingredient used primarily as a humectant and preservative booster in skincare formulations, known for its hydrating benefits and low irritancy profile.

Capsaicin

Capsaicin is a potent TRPV1 agonist used topically for analgesia (often ~0.025–0.1% in creams and up to 8% in patches) and is intrinsically noxious to skin, commonly causing intense burning, stinging, erythema, and neurogenic inflammation even at low concentrations. Clinical experience and labeling for capsaicin products consistently reflect frequent, expected irritation and discomfort, which is amplified in eczema, barrier-compromised, or post-procedure skin. Given the predictable high irritation burden and risk of severe flare in sensitive populations, it warrants the maximum irritancy score. Safety Notes: In consumer skincare, capsaicin is typically used at extremely low levels in “warming/tingling” leave-on creams, massage gels, and lip-plumping style products, with the lowest marketed formulas often around ~0.5 ppm (0.00005%) to deliver a perceptible sensory effect while limiting irritation. High-strength OTC topical analgesic/rubefacient creams and patches available to the general public commonly use about 0.025–0.1% capsaicin, with ~0.1% representing the upper end seen in non-prescription products; higher percentages (e.g., 8%) are generally restricted to prescription/professional use and are excluded. Rinse-off cosmetics rarely use meaningful capsaicin levels due to irritation risk and limited benefit, so the observed market range is driven primarily by leave-on products.

Caramel

Caramel (caramel color) is primarily a coloring agent used at low concentrations and is generally well-tolerated on skin, with irritation uncommon in routine cosmetic use. However, it is a complex mixture formed by sugar heating and can contain reactive byproducts/impurities depending on manufacturing, so mild irritant or contact reactions are possible in highly reactive or eczema-prone individuals. Given the variability and my safety-first approach for compromised barriers, I rate it as gentle but not inert. Safety Notes: Caramel (caramel color) is most often used as a colorant in skincare, where it appears at trace-to-low levels (about 0.001–0.1%) in leave-on lotions/serums and rinse-off cleansers to tint product appearance without staining skin. Higher levels are observed in strongly tinted body washes, scrubs, and self-tan/bronzing or glow products where caramel contributes visible brown tone, commonly ~0.5–3% and occasionally up to ~5% in consumer OTC formulas. No specific EU/FDA cosmetic maximum is generally set for caramel color itself, so practical limits are driven by shade intensity, stability, and potential for unwanted coloration/transfer.

Carapa Guaianensis Seed Oil

Carapa guaianensis (andiroba) seed oil is an emollient lipid used typically at a few percent up to higher levels in balms, and like other botanical oils it is generally well-tolerated but not inert. Clinical experience and patch-testing literature for plant oils supports occasional irritant or allergic contact dermatitis in reactive/eczema-prone patients (from minor constituents/oxidation products), so I score it as mild rather than “gentle” for compromised skin. Safety Notes: Carapa guianensis (andiroba) seed oil is used at very low levels (~0.05–0.5%) as a supportive emollient in emulsions (lotions/creams) or as part of a botanical lipid blend where it is not a key claim ingredient. In mainstream leave-on body butters, balms, and facial oils it is commonly formulated around 1–20% depending on the oil phase and sensory targets, while consumer-available single-ingredient oils and anhydrous blends marketed as “100% andiroba oil” reach 100% (neat oil); rinse-off products typically sit at the lower end due to cost and deposition limits.

Carbomer

MVP Approved - Carbomer is a synthetic polymer used primarily to thicken, stabilize, and improve the texture of cosmetic formulations, with little to no active benefit on the skin and a very low propensity for irritation.

Cardiospermum Halicacabum Flower/Leaf/Vine Extract

Cardiospermum halicacabum (balloon vine) extract is primarily used as a soothing/anti-inflammatory botanical in leave-on products, typically at low concentrations (~0.1–2%). While generally well-tolerated and sometimes used in eczema-prone skin, botanical extracts can still trigger irritant or allergic contact dermatitis in a minority of highly reactive patients due to complex, variable plant constituents. Given this sensitization potential despite its calming intent, a gentle-but-not-zero risk score is most appropriate for patient safety. Safety Notes: In commercial skincare, Cardiospermum halicacabum extract is most often used as a soothing/anti-redness botanical at very low levels when it is part of a multi-extract complex or a standardized supplier blend, with finished-product inclusion commonly starting around 0.001–0.05% (especially in leave-on moisturizers/serums for sensitive skin and some rinse-off cleansers). Higher-strength consumer OTC products (typically leave-on balms, barrier creams, or “eczema/itch relief”-positioned cosmetics) sometimes use single-botanical dosing around 1–3%, and a practical upper end observed in marketed formulas is ~5% due to color/odor, stability, and irritation/sensory constraints rather than regulatory limits.

Carica Papaya Leaf Extract

Carica papaya leaf extract is a botanical antioxidant/soothing additive typically used at low percentages, but papaya-derived materials can contain proteolytic enzymes and diverse plant constituents that increase sting and irritant contact dermatitis risk in reactive or barrier-impaired skin. Clinical patch-test experience with botanical extracts shows a non-trivial rate of irritation/sensitization despite “gentle” marketing, so I score it as mild with occasional sensitivity possible, especially in eczema-prone users or when layered with other actives. Safety Notes: In mass-market leave-on skincare (creams/lotions/serums) and rinse-off cleansers, papaya leaf extract is often used at very low levels (~0.0005–0.1%) as part of botanical blends where the extract is present mainly for marketing/antioxidant/soothing positioning. More performance-positioned OTC products (e.g., brightening/anti-acne serums, masks, and “natural actives” treatments) commonly use ~0.5–3% of standardized liquid or powder extracts, while a small number of consumer-available specialty formulations (especially masks/spot gels or products built around a single hero botanical) reach about 5–10% extract depending on solvent system and raw-material strength; there is no specific EU/FDA maximum, so the upper end is driven by stability, odor/color, and skin tolerance rather than regulation.

Carnitine

Carnitine (L-carnitine) is a water-soluble conditioning/sebum-modulating ingredient typically used at low concentrations (~0.1–2%) and is not inherently caustic or pH-dependent like acids. Human irritation and sensitization reports are uncommon in cosmetic use, but as a biologically active zwitterionic amino-acid derivative, it can occasionally sting on compromised barriers (eczema/post-procedure) when layered with other actives. Given sensitive-skin safety priorities, I rate it very gentle rather than exceptionally gentle. Safety Notes: In commercial cosmetics, carnitine (often listed as Carnitine or L-Carnitine) is most commonly used as a sebum-modulating/“oil control” and skin-conditioning active in leave-on serums, toners, and moisturizers, where low-end usage appears around 0.01–0.1% as a minor supportive active. Mainstream leave-on oil-control products frequently sit around ~0.5–2%, while the upper end observed in consumer-available “high strength” anti-oil/anti-blemish formulations reaches about 3% (higher levels are uncommon due to formula feel, solubility/ionic strength, and diminishing practical benefit). Rinse-off products typically use it at the lower end of the range because of brief contact time, whereas the highest levels are primarily seen in leave-on products.

Carnosine

Carnosine is a naturally occurring dipeptide used in skincare primarily as an antioxidant/anti-glycation agent, typically at low concentrations (about 0.1–1%), and it is generally well tolerated in leave-on products. Available human data and widespread cosmetic use suggest a low rate of irritation or sensitization compared with acids, retinoids, fragrances, or more reactive preservatives. For highly reactive or eczema-prone patients, mild stinging can still occur depending on the overall formula (pH, solvents, other actives), but the ingredient itself is best classified as very gentle. Safety Notes: In commercial anti-aging/anti-glycation serums and moisturizers, carnosine is commonly used at very low levels (around 0.01–0.1%) as a supportive antioxidant/anti-glycation active, and it also appears at these trace levels in some multi-ingredient formulas. Higher-strength consumer-available leave-on treatments (serums/ampoules) have been marketed around ~1–2% carnosine, which is near the practical upper end due to solubility, cost, and formulation constraints; rinse-off products, when they include it, are typically at the low end because of limited contact time. No specific EU/FDA cosmetic maximum is set for carnosine, so the observed range is primarily market- and stability-driven.

Carrageenan

Carrageenan is a sulfated polysaccharide used primarily as a thickener/gel former in leave-on and rinse-off products, typically at low concentrations (about 0.1–2%). In human topical use it is generally well tolerated and not a common irritant or sensitizer in patch testing, but as a high–molecular weight film former it can occasionally contribute to stinging/tight-feel in very reactive or barrier-impaired skin when layered with other potential irritants. Given its low intrinsic reactivity yet non-zero risk in compromised eczema-prone populations, it fits best as very gentle rather than completely inert. Safety Notes: In commercial skincare, carrageenan is most commonly used as a secondary thickener/stabilizer in rinse-off cleansers, shower products, and some leave-on gels/lotions at very low levels (~0.01–0.2%) to support viscosity and suspension. Higher concentrations are found in consumer-available gel masks, peel-off/film-forming masks, and thixotropic gel textures where carrageenan functions as a primary gellant, with real-world formulas reaching ~1–3% depending on carrageenan type/blend and the presence of other gums/salts. Above ~3% is uncommon in OTC cosmetics because gels can become overly rigid/stringy and harder to process/package, so most market products cap around this level.

Carthamus Tinctorius Seed Oil

Carthamus Tinctorius (safflower) seed oil is primarily an emollient used at moderate-to-high concentrations in leave-on products, and it is generally well tolerated with low irritancy in patch testing for most users. However, like many plant-derived oils it can rarely trigger irritation or contact allergy in highly reactive or eczema-prone patients (often influenced by oxidation/impurities), so it is not truly inert. Given typical real-world use and sensitive-skin safety considerations, it fits best as very gentle rather than exceptionally gentle. Safety Notes: In commercial leave-on skincare, safflower (Carthamus tinctorius) seed oil is frequently used at low levels (~0.1–2%) as an emollient/lipid-replenishing co-oil in creams, lotions, and serums, and in rinse-off cleansers it may appear at similar trace-to-low levels mainly for skin feel. At the high end, consumer-available facial/body oils and “100% safflower oil” single-ingredient products are sold at 95–100% (with 100% common when it is the sole INCI-listed ingredient), reflecting the full observed OTC market range.

Casein

Casein is a milk-derived protein used as a film-former/conditioning agent in cosmetics, typically at low concentrations, and it is not intrinsically caustic like acids or retinoids. However, as a high–molecular weight animal protein, it has documented potential to trigger reactions in a subset of users with milk protein allergy or highly compromised eczema skin via contact urticaria or eczematous flares, even when overall population irritation rates are low. Given this sensitization/allergy risk in sensitive populations, I score it as mild rather than gentle for patient safety. Safety Notes: In modern commercial skincare, casein (a milk-derived protein) appears infrequently and typically as a minor film-forming/skin-conditioning additive in “milk protein” themed lotions, creams, and masks at trace-to-low levels (~0.01–0.5%). The highest consumer-available uses are seen in specialty rinse-off masks/cleansers and some leave-on creams marketed around milk proteins where the total milk-protein complex can reach a few percent; casein itself is typically formulated up to about 5% before odor, allergen labeling considerations, and solubility/texture constraints become limiting. No specific FDA/EU cosmetic maximum is set for casein, so the practical upper end is driven mainly by stability and sensorial limits rather than regulation.

Cassia Angustifolia Seed Polysaccharide

Cassia Angustifolia Seed Polysaccharide is a film-forming, humectant polysaccharide used at low concentrations (typically ~0.1–2%) to improve hydration and skin feel. As a high–molecular weight sugar polymer, it is generally non-reactive and not a common irritant in patch testing, with irritation more likely due to formula context or contamination rather than the polysaccharide itself. For highly sensitive or eczematous skin, rare intolerance to film formers is possible, so it is best categorized as very gentle rather than completely inert. Safety Notes: In commercial leave-on skincare (serums, moisturizers, eye products), Cassia Angustifolia Seed Polysaccharide is commonly used as a film-forming/instant tightening and smoothing polymer at low levels around 0.05–0.3% to provide a subtle sensory and soft-focus effect without tack. Higher-strength consumer products marketed for “instant lift” or “firming” effects and some peel-off/film-forming masks use it more aggressively, typically ~0.5–2.0%, with ~2% representing the upper end before viscosity, tack, and film brittleness become limiting; rinse-off products generally sit toward the low-to-mid portion of this range.

Castanea Crenata Shell Extract

Castanea crenata (Japanese chestnut) shell extract is typically used at low concentrations as an antioxidant/astringent, often rich in polyphenols and tannins. While generally tolerated in many users, tannin-heavy botanical extracts can provoke stinging, dryness, or flare reactions in eczema-prone or barrier-compromised skin, and botanical extracts carry some risk of delayed sensitization. Given the limited standardized clinical irritation data and the known reactivity of astringent botanicals in sensitive populations, a mild (0.4) irritancy score is the safest clinically aligned assessment. Safety Notes: In commercial skincare, Castanea crenata (Japanese chestnut) shell extract is most often used as a minor botanical active in leave-on toners/serums/creams, where it commonly appears at trace-to-low levels around 0.001–0.1% as part of multi-extract blends. Higher-strength consumer products (typically brightening/antioxidant or “pore/texture” serums and ampoules, and some wash-off masks) can push the neat extract to ~0.5–3% depending on extract carrier/standardization and color/odor constraints. No specific global cosmetic maximum is established for this INCI; practical upper limits are mainly driven by sensory impact, solubility/compatibility, and stability rather than regulation.

Castanea Sativa Leaf Extract

Castanea sativa (chestnut) leaf extract is a botanical antioxidant/astringent ingredient typically used at low percentages, but it contains polyphenols/tannins that can sting or provoke dryness on compromised barriers. While not a common primary irritant in population patch testing, botanicals have meaningful variability and can trigger irritant reactions in eczema-prone or highly reactive patients, especially in leave-on products. Given the potential for barrier-tightening astringency and unpredictable plant-extract sensitivity, a mild score is the safest clinically-aligned assessment. Safety Notes: In commercial skincare, Castanea Sativa (Chestnut) Leaf Extract is most often used as a minor antioxidant/soothing botanical at very low levels (trace to ~0.1%) in leave-on toners, lotions, and cleansers, where it functions mainly as a label-claim extract within a broader botanical blend. Higher-strength consumer products (e.g., targeted anti-redness/antioxidant serums or ampouled concentrates) can reach ~1–3% when the extract is a primary featured active, with levels above this being uncommon due to solubility, color/odor, and stability/sensory constraints. There are no specific EU/FDA maximum limits for this botanical extract in cosmetics, so the observed range is driven primarily by typical supplier use-level guidance and real-world formulation practicality.

Castanea Sativa Seed Extract

Castanea Sativa (chestnut) seed extract is primarily used as an antioxidant/soothing plant extract, typically included at low concentrations (often <1–2%) in leave-on skincare. While not a strong “active” like acids or retinoids, botanical extracts can still trigger stinging or allergic contact dermatitis in a small subset of highly reactive or eczema-prone patients due to naturally occurring polyphenols/proteins and variable raw-material composition. Given its generally good tolerability but non-zero sensitization potential in compromised skin, it fits best as a gentle ingredient with minimal but real risk. Safety Notes: In mass-market leave-on products (creams/serums/toners), Castanea Sativa (Chestnut) Seed Extract is most often used as a minor botanical active or part of a multi-extract blend, commonly appearing at very low levels around 0.0005–0.05% as supplied/active (especially when the INCI represents a dilute glycerin/propylene glycol extract). Higher-strength consumer products marketed for antioxidant/firming/anti-glycation benefits and some mask/ampoule-style formulations can reach ~1–5% of the extract material, with practical upper limits driven by solubility, color/odor, and formula stability rather than specific regulatory caps (no specific EU/FDA concentration limit observed for this INCI).

Castor Isostearate Succinate

Castor Isostearate Succinate is a castor-oil–derived ester used mainly as an emollient/surfactant in rinse-off and leave-on products, typically at low-to-moderate concentrations. As a high–molecular weight, non-volatile lipid derivative, it is generally well-tolerated and not a common cause of irritant dermatitis in patch testing, though very reactive or barrier-impaired eczema patients can occasionally sting or flare with any surfactant-like ester. Given the low inherent reactivity but nonzero risk in compromised skin, a very gentle score is most appropriate. Safety Notes: In commercial skincare and cosmetics, Castor Isostearate Succinate is typically used as an emollient/texture modifier and pigment-wetting/binder component, appearing at low levels (~0.1–1%) in creams/lotions and color cosmetic-type hybrid skincare where it fine-tunes slip and payoff. Higher levels (5–15%) are observed in anhydrous balms, stick products, cleansing balms, and some oil-based makeup removers where it contributes significant structuring, glide, and solubilization/wetting of oils and waxes. Use levels are generally higher in leave-on anhydrous systems than in rinse-off emulsions, and are constrained mainly by desired viscosity/sensory rather than specific regulatory maximums.

Castor Oil/Ipdi Copolymer

Castor Oil/IPDI Copolymer is a film-forming polymer (castor oil modified with isophorone diisocyanate) typically used at low percentages to improve texture and wear; once reacted, it behaves as an inert emollient/resin with low irritancy in routine patch testing. The main safety consideration is rare sensitivity in highly reactive individuals to residual monomers/impurities, but at typical cosmetic concentrations it is generally well tolerated and not intrinsically irritating, supporting a very gentle score. Safety Notes: Castor Oil/IPDI Copolymer is most often used as an oil-gellant/viscosity builder and film-forming structurant in anhydrous leave-on systems (lip oils/glosses, balms, stick products) and appears at low levels (~0.1–1%) when used only to boost payoff, gloss, and stability. In consumer lip oils, glosses, and high-structure balms/sticks it is commonly in the ~5–15% range, and the strongest OTC products that rely on it as a primary structuring resin/gellant can reach ~20–25% in anhydrous formats; rinse-off products, when used, are typically at the low end due to limited benefit and build-up concerns.

Cedrus Atlantica Bark Extract

Cedrus atlantica bark extract is a fragrant botanical material closely associated with cedarwood constituents (terpenes) that are well-recognized triggers for irritation and allergic contact dermatitis, especially in eczema-prone and barrier-impaired skin. Even at the low concentrations typically used for scent/marketing (often well under 1%), cumulative exposure in leave-on routines and the presence of fragrance allergens make clinically meaningful reactions plausible. Given the sensitization risk profile of aromatic plant extracts, I score it as a significant irritant requiring avoidance or very cautious use in highly sensitive populations. Safety Notes: In commercial skincare, Cedrus Atlantica (Atlas cedar) bark extract is most often used as a minor botanical add-in or part of a blend, commonly appearing in leave-on creams/serums and rinse-off cleansers at trace levels (~0.0001–0.05%) mainly for marketing/skin-feel/fragrance-adjacent positioning. Higher-strength consumer products (typically niche botanical serums, scalp/blemish-targeting treatments, and “active botanical” emulsions) can reach ~0.5–2% when the extract is used as a featured functional botanical, though levels above ~2% are uncommon due to odor/color impact and irritation/sensitization risk typical of resinous cedar-derived materials. No specific EU/FDA maximum is set for this INCI extract, so practical market limits are driven by supplier use-level guidance and tolerability in leave-on formats.

Cellulose

Cellulose is a plant-derived polysaccharide used primarily as a thickening agent, film-former, and absorbent in concentrations typically ranging from 0.1-5%. Clinical patch testing data consistently shows cellulose to be non-irritating and non-sensitizing, with exceptional tolerability even in compromised skin populations including post-procedure and atopic dermatitis patients. Its large molecular structure prevents penetration, and it functions as an inert structural component with no known biochemical activity that could trigger inflammation or immune responses. Safety Notes: Cellulose and its derivatives (microcrystalline cellulose, cellulose gum) appear in commercial skincare products across a wide concentration spectrum. At the low end (0.1-1%), cellulose functions as a minor thickener or texture modifier in serums and lightweight lotions. At the high end (10-15%), it serves as a primary rheology modifier and film-former in specialized products like peel-off masks, mattifying primers, and oil-absorbing formulations where substantial structure and absorbency are required. Both leave-on and rinse-off products utilize the full range depending on the desired texture and performance characteristics.

Cellulose Gum

Cellulose gum (carboxymethylcellulose) is primarily a thickener/stabilizer, typically used at low concentrations (~0.1–2%), and is generally considered biologically inert on skin. Clinical experience and patch-test data indicate a very low rate of irritation or sensitization, though rare contact reactions can occur, especially on severely compromised barriers. Given the need to avoid underestimating risk in highly reactive eczema populations, it fits best as exceptionally gentle rather than completely inert. Safety Notes: In commercial skincare, cellulose gum (carboxymethylcellulose) is commonly used as a secondary rheology modifier/suspension aid at very low levels (~0.05–0.3%) in lotions, serums, and cleansers, where it subtly boosts viscosity and stabilizes insoluble actives. The highest consumer-available levels are seen in thick gel products (e.g., peel-off/mask gels, aloe-style gels, some wash-off treatments) where it can serve as a primary gellant/film former, typically reaching ~1–2.5% before texture becomes overly stringy/tacky or difficult to process; rinse-off formats more often sit at the lower-to-mid part of the range while leave-on gels/masks more often occupy the upper end.

Centella Asiatica Extract

Centella asiatica extract is primarily a soothing/anti-inflammatory botanical (often used around ~0.1–5% in leave-on products) and is generally well tolerated, including in compromised skin when the formula is otherwise simple. 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 with higher extract loads or impurity/solvent residues. Given this low-but-real sensitization potential, it scores as gentle rather than very gentle or inert. Safety Notes: Across mass-market and dermocosmetic products, Centella asiatica extract is often included at very low levels (around 0.01–0.1%) primarily for marketing/soothing claims, especially in rinse-off cleansers and lower-cost lotions. Most leave-on toners/serums/creams commonly sit in the ~0.1–5% range, while high-strength consumer “cica” ampoules and concentrated soothing gels frequently disclose 10–25% Centella extract (noting this is typically a supplier extract solution rather than purified actives like madecassoside). Centella extracts are not specifically concentration-limited by major cosmetic regulations, so the upper end is mostly set by stability, sensory impact, and supplier solvent system rather than legal caps.

Centella Asiatica Flower/Leaf/Stem Extract

Centella asiatica extract is primarily a soothing/anti-inflammatory botanical used at low concentrations, and in most clinical and consumer use it is well tolerated on sensitive and eczema-prone skin. However, as a multi-component plant extract (including triterpenes and other phytochemicals), it has a small but real risk of irritant or allergic contact dermatitis in reactive individuals, especially with repeated exposure or in compromised barriers. Given this non-zero sensitization potential despite its calming reputation, it fits best as a generally gentle ingredient rather than exceptionally gentle. Safety Notes: In mass-market leave-on products (creams/lotions/cleansers), Centella Asiatica Flower/Leaf/Stem Extract is often used as a label-level soothing botanical at very low levels (~0.001–0.05%), especially when paired with other extracts. Mid-range serums and barrier creams commonly use ~0.1–5% depending on extract carrier/standardization. High-strength consumer-available “cica/centella” ampoules and mask essences can reach ~10–20% extract solution (often not standardized for asiaticoside/madecassoside and sometimes glycerin/propylene glycol/water-based), with rinse-off products typically sitting lower than leave-on formats due to cost and limited contact time.