Skincare Ingredients

Pseudozyma Epicola/Camellia Japonica Seed Oil Ferment Extract Filtrate

This is a fermented botanical/oil-derived filtrate primarily used at low concentrations as a conditioning/skin-feel and barrier-support ingredient; it is not an exfoliating acid or high-potency active. While camellia derivatives are generally well-tolerated, fermentation byproducts and residual yeast-related components can occasionally provoke stinging or dermatitis in highly reactive or eczema-prone individuals, so it is best classified as gentle rather than very gentle/inert. Safety Notes: In commercial skincare, this type of ferment filtrate is most often used as a minor supporting humectant/conditioning active in leave-on emulsions and essences, with low-end inclusion commonly around 0.01–0.1% (often consistent with supplier-recommended use levels for fermentation-derived extracts). High-strength consumer products that feature the ferment as a highlighted key ingredient (especially watery essences/serums and barrier-support formulas) can push into the 1–5% range, which is typically near the practical upper end before cost, odor/color, and preservation/stability constraints become limiting. It is less common in rinse-off products and generally appears at lower levels there because of short contact time.

Psidium Guajava Fruit Extract

Psidium guajava (guava) fruit extract is primarily used as an antioxidant/soothing botanical at low concentrations, but as a complex plant mixture it contains multiple bioactive compounds (e.g., polyphenols and small aromatic constituents) that can provoke stinging or dermatitis in a reactive subset. Clinical patch-test data for guava fruit extract specifically is limited, and botanical extracts show higher real-world variability (batch differences, solvents, co-extractives) than single-ingredient humectants, so I score it as mild with occasional sensitivity possible, especially in eczema-prone skin and when layered with other actives. Safety Notes: In mass-market and prestige cleansers/toners/lotions, Psidium Guajava Fruit Extract is commonly used as a minor antioxidant/botanical support ingredient at trace-to-low levels (often ~0.001–0.1% active extract, frequently reflecting a diluted supplier solution). In consumer leave-on serums, masks, and “brightening/antioxidant” products marketed around guava, formulas can push into the 1–5% range using standardized extracts or higher-load botanical blends, with stability, color/odor, and tack typically limiting further increases. Rinse-off products generally sit at the lower end because contact time is short and botanicals are often included mainly for positioning rather than primary efficacy.

Psidium Guajava Seed Oil

Psidium Guajava (guava) seed oil is primarily an emollient/occlusive lipid used at low-to-moderate levels to support barrier function, but as a botanical oil it contains minor unsaponifiables that can provoke irritation or allergy in reactive or eczema-prone skin. Clinical patch-test data for this specific oil is limited, so safety assessment relies on its class behavior: most seed oils are generally tolerated yet have a meaningful minority of sensitization/irritation reports compared with inert carriers. Given the uncertainty and the higher-risk population, I rate it as mild—usually tolerated, but occasional sensitivity is plausible and patch testing is prudent. Safety Notes: In mass-market and indie formulations, Psidium Guajava Seed Oil most often appears as a minor emollient/marketing botanical in blends at trace-to-low levels (~0.01–0.5%), especially in lotions, shampoos/conditioners, and facial serums where it is one of many plant oils. At the high end, consumer-available single-ingredient guava seed oil products (sold as 100% pure oil) and anhydrous balms/oil serums can reach 50–100%, with 100% representing the neat oil; regulatory frameworks generally do not set a specific maximum for this cosmetic plant oil, so practical limits are driven by sensorial feel, oxidation management, and leave-on wearability rather than legal caps.

Ptychopetalum Olacoides Bark/Stem Extract

Ptychopetalum olacoides (muira puama) bark/stem extract is a botanical extract typically used at low concentrations for conditioning/“energizing” claims, but it contains multiple bioactive phytochemicals (e.g., terpenoids/phenolics) that can act as irritants or sensitizers in reactive skin. Robust, standardized human irritation/sensitization data are limited, and variability between extract preparations increases unpredictability, especially for eczema-prone patients. Given the uncertainty and the higher risk profile of complex botanicals compared with inert humectants, a moderate irritancy score is warranted and patch testing is advisable. Safety Notes: In commercial cosmetics, Ptychopetalum olacoides (Muira Puama) bark/stem extract is most often used as a minor botanical component in multi-extract blends for anti-aging/firming or scalp/hair-tonic positioning, where finished-product levels can be as low as ~0.0005–0.05% (especially when supplied in diluted glycerin/propylene glycol carrier systems). Higher-end consumer leave-on serums, eye products, and scalp tonics occasionally use it as a featured extract at ~0.5–2.0% finished-product level, with 2% representing the upper end observed for OTC products due to cost, odor/color, and sensitization/stability constraints. This ingredient is predominantly seen in leave-on formats; rinse-off products typically sit at the low end because deposition and marketing driver levels are lower.

Pueraria Lobata Root Extract

Pueraria lobata (kudzu) root extract is a botanical antioxidant/soothing extract typically used at low concentrations, and it is not a common primary irritant like acids or surfactants. However, like many plant extracts it contains multiple bioactive compounds (e.g., isoflavones) that can trigger irritation or allergic contact dermatitis in a small but meaningful subset of highly reactive or eczematous patients, especially in leave-on products. Given the variability in extract composition and the heightened risk in compromised skin, I rate it as mild rather than “gentle.” Safety Notes: In mass-market and prestige leave-on skincare, Pueraria lobata (kudzu) root extract is most often used as a minor botanical supporting ingredient, frequently appearing at trace-to-low levels around 0.0001–0.1% when added via multi-extract blends or preserved glycerin/butylene glycol extracts. Dedicated “phytoestrogen/brightening/firming” serums and concentrated botanical/Asian beauty formulas marketed to consumers can use it at much higher active levels, commonly ~0.5–2% and occasionally up to about 5% when the INCI is supplied as a standardized dry extract or high-solids extract. Rinse-off products (cleansers/body wash) typically sit toward the low end due to short contact time and cost, while higher levels are primarily observed in leave-on serums/creams; no specific EU/FDA maximum is set for this botanical, so practical stability/irritation and supplier-use guidance drive the upper bound.

Pullulan

Pullulan is a high–molecular weight polysaccharide film-former used at low concentrations (typically ~0.1–5%) to provide a smoothing/tightening feel and improve texture; it is not an active and does not meaningfully alter skin pH. Clinical use and patch-test experience generally show very low irritation/sensitization potential, but in severely compromised barriers (e.g., active eczema) any film-former can occasionally sting or feel tight/occlusive when layered with other products. Given the overall benign profile yet non-zero reactivity risk in highly sensitive populations, a very gentle score is most appropriate. Safety Notes: In commercial skincare, pullulan is most often used as a film-forming/skin-tightening polymer at very low levels (typically ~0.05–1%), and I have observed it listed down around ~0.01% in multi-polymer serums/essences where it functions as a minor texture/film modifier. At the high end, consumer-available “instant lift,” peel-off/film mask, and tightening gel products can use pullulan at several percent, with the strongest OTC film-forming/peel-type formulations reaching about ~10% to create a robust continuous film. Leave-on products generally sit in the low-to-mid range due to tack/feel constraints, while higher percentages are most common in film-mask formats where tack and peel/film formation are desired.

Pumice

Pumice is an insoluble mineral abrasive used in scrubs, soaps, and foot/body exfoliants, and its irritancy risk is driven by mechanical friction rather than chemical reactivity. In sensitive or eczematous skin, abrasive particles can create microtears and barrier disruption, commonly provoking stinging, erythema, and flare-ups—especially with frequent use or concurrent actives (acids/retinoids). Because this injury mechanism is predictable and clinically relevant in compromised skin, it warrants a significant irritancy score despite low sensitization potential. Safety Notes: In commercial skincare, pumice appears at very low levels (~0.1–1%) in gentle daily facial scrubs/cleansers where it functions as a light physical exfoliant alongside other abrasives or polymers. Typical rinse-off body/foot scrubs commonly use ~5–30% depending on desired scrub intensity and viscosity. The highest consumer-available concentrations are found in anhydrous or paste-like heavy-duty foot/hand “pumice scrub” products and mechanic-style cleansers where pumice can be the dominant solid phase (about 50–80%); it is overwhelmingly used in rinse-off formats due to grit/abrasion and poor suitability for leave-on products.

Punica Granatum Extract

Punica granatum (pomegranate) extract is primarily used as an antioxidant/soothing botanical at low concentrations (often <1–2%), and is generally well tolerated. However, as a complex plant extract containing multiple polyphenols and other constituents, it carries a real risk of irritation or allergic contact dermatitis in reactive or eczema-prone patients, particularly in leave-on products and when combined with other actives. Given this sensitization potential despite “gentle” marketing, I rate it as mild rather than gentle. Safety Notes: In mass-market leave-on creams/serums and rinse-off cleansers, Punica Granatum (pomegranate) extract is commonly used as an antioxidant/marketing botanical at low, label-supporting levels around 0.01–0.1%, especially when supplied as a standardized, carrier-diluted extract. High-strength consumer products (antioxidant serums, treatment masks, and some “natural/organic” emulsions) can reach ~1–5% when using glycerin/propylene glycol/water extracts or concentrated standardized extracts, with higher levels mainly constrained by color/odor, tannin-driven astringency, and stability/compatibility rather than regulation.

Punica Granatum Fruit Extract

Punica granatum (pomegranate) fruit extract is primarily an antioxidant/soothing botanical used at low percentages, but it is a complex mixture of polyphenols and other plant constituents that can trigger stinging or dermatitis in reactive or eczematous skin. Clinical experience and patch-test data for botanicals show a non-zero rate of irritation/sensitization, especially in compromised barriers or when combined with other actives. Given patient-safety concerns for highly sensitive populations, I score it as mild irritancy rather than categorizing it as universally gentle. Safety Notes: In mass-market lotions, cleansers, and toners, Punica Granatum (Pomegranate) Fruit Extract is often used as a minor antioxidant/marketing botanical at very low levels (~0.001–0.1%) due to supplier recommended use rates and cost/odor/color constraints. In more “active” antioxidant serums, masks, and premium creams (leave-on especially), products commonly reach ~0.5–2%, with a small set of consumer-available high-botanical formulations using ~3–5% when the extract is standardized and the formula is built to manage color/tannin odor and stability. Rinse-off products typically sit toward the lower end because contact time is short, while higher levels are more often observed in leave-on products.

Punica Granatum Pericarp Extract

Punica granatum (pomegranate) pericarp extract is used mainly as an antioxidant/astringent botanical, typically at low percentages, but it contains polyphenols/tannins that can be mildly irritating and drying on compromised barriers. Patch-test and real-world use data for botanical extracts show occasional irritation or contact dermatitis in reactive/eczema-prone individuals, especially in leave-on formulas or when combined with other actives. Given the variability of botanical composition and the higher risk in sensitive skin populations, a mild (0.4) score best reflects patient-safety expectations. Safety Notes: In mass-market leave-on skincare (creams/lotions/serums) and rinse-off cleansers, pomegranate pericarp extract is frequently used at trace to low levels (~0.001–0.1%) as an antioxidant/marketing botanical, often within multi-extract blends. More concentrated consumer-available “antioxidant” or “polyphenol” serums and masks use standardized pericarp extracts at higher active loading, typically ~0.5–3% and occasionally up to ~5% when the extract is formulated for topical use and color/odor/tannin astringency are managed. There is no specific FDA/EU maximum limit for this botanical extract, so the upper bound is constrained mainly by sensory, staining, and stability rather than regulation.

Punica Granatum Seed Oil

Punica Granatum (pomegranate) Seed Oil is an emollient lipid used in leave-on products typically around ~1–10% (sometimes higher) to reduce TEWL and support barrier comfort. As a non-volatile plant oil it is generally well tolerated, but like many botanical oils it can still trigger irritation or contact allergy in a small subset of highly reactive or eczema-prone patients due to natural minor constituents/oxidation byproducts. Overall risk is low but not zero, so it fits a "gentle" profile rather than exceptionally gentle. Safety Notes: In mass-market leave-on skincare (lotions, creams, serums) Punica Granatum Seed Oil is often used as a minor emollient/antioxidant component at trace-to-low levels (~0.01–0.5%) when positioned as a supporting botanical, with many formulas clustering around ~0.5–5%. At the high end, consumer-available facial oils and “pure oil” offerings are sold as 100% Punica Granatum Seed Oil, and anhydrous oil blends can also use it at very high levels (e.g., 10–50%) when it is the featured lipid. Rinse-off products (cleansers/body washes) typically sit at the low end due to short contact time and cost, while leave-on oils/serums account for the upper end; there is no specific FDA/EU maximum restriction beyond general cosmetic safety and stability considerations.

Pvm/Ma Copolymer

PVM/MA copolymer is a high–molecular weight film-forming polymer used in hair styling products and some skincare/makeup (typically ~0.5–10%) to improve hold, texture, and wear. As an inert polymer it has low inherent irritancy and is generally well tolerated in patch testing, but the occlusive film can increase sting/tightness or trapping of other irritants on highly reactive or eczematous skin, especially with leave-on use. Given this small but real risk in compromised barriers, I rate it as gentle rather than exceptionally gentle. Safety Notes: In commercial skincare, PVM/MA Copolymer is most often used as a film former/binder and rheology aid, showing up at very low levels (~0.05–0.3%) in leave-on lotions/serums and rinse-off cleansers mainly to improve slip, deposition, and feel. Higher levels are found in consumer-available peel-off masks, long-wear setting/primer-type products, and styling-film skincare hybrids where strong film formation is needed, with real-world use commonly 2–6% and observed up to ~8% in high-hold film-forming formulas (typically leave-on/peel-off rather than simple emulsions).

Pvm/Ma Decadiene Crosspolymer

PVM/MA Decadiene Crosspolymer is a high–molecular weight film-forming/thickening polymer used at low concentrations to stabilize formulas and improve texture, and it is not a bioactive ingredient. Patch-test and clinical use experience with similar PVM/MA crosspolymers suggest a low rate of irritation, with reactions typically limited to rare cases in highly compromised or very reactive skin due to occlusion/film effects or formula context rather than inherent chemical reactivity. Given the sensitive-skin population and the need to avoid underestimating risk, it fits best as very gentle rather than completely inert. Safety Notes: PVM/MA Decadiene Crosspolymer is a film-forming, rheology/texture-modifying polymer most often used at low levels in leave-on skincare (serums, primers, moisturizers) to add slip, reduce tack, and improve wear; commercial products commonly include it around 0.05–0.5% as part of a broader polymer system. Higher-strength consumer-available products such as long-wear primers, setting/“grip” gels, and some peel-off or high-film-former masks can push total use levels into the 1–5% range to maximize film formation and hold, with practical upper limits driven by viscosity, pilling/flake risk, and sensory tack rather than a specific global regulatory cap.

Pvp

PVP (polyvinylpyrrolidone) is a film-forming binder/fixative used in cosmetics (e.g., hair sprays, mascaras, skincare) typically around ~0.1–5%, and it is generally well tolerated because it is a large, non-reactive polymer with minimal skin penetration. Clinical experience and patch-test data suggest low irritancy overall, though occasional stinging/irritant reactions can occur from film formation/occlusion or impurities and in highly compromised barriers (e.g., eczema), so I do not classify it as fully inert. Safety Notes: In consumer skincare and personal care, PVP (polyvinylpyrrolidone) is most often used as a film former/binder or styling-fixative polymer, with very low levels (~0.05–0.5%) appearing in leave-on lotions/serums and some cleansers to aid feel, adhesion, or film formation. Mid-range usage (~1–5%) is common in peel-off masks and certain long-wear or water-resistant leave-on formats where a stronger polymer film is desired. The highest OTC levels observed are in high-hold film-forming products (e.g., peel-off masks and adjacent consumer cosmetics/personal care fixatives) where PVP can reach ~10–15% depending on grade/viscosity targets; it is not specifically concentration-restricted by FDA/EU, with practical limits driven by tack, flaking, and solubility/viscosity.

Pyrus Communis Fruit Extract

Pyrus Communis (pear) fruit extract is typically used at low concentrations as a conditioning/antioxidant “botanical” additive, but fruit-derived extracts are complex mixtures that can include naturally occurring acids, sugars, and trace aromatic compounds that increase irritation variability versus purified humectants. Clinical patch-test literature generally suggests low-to-moderate irritancy for most users, yet reactive/eczema-prone patients can experience stinging or dermatitis from botanicals, so I score it as mild rather than inherently gentle for compromised skin safety. Safety Notes: In commercial skincare, Pyrus Communis (Pear) Fruit Extract is most often used as a minor botanical “label claim” component in leave-on lotions/serums and rinse-off cleansers at trace levels (~0.001–0.1%), especially when supplied as a dilute extract in a solvent/glycerin base. Higher-end botanical- or “fruit extract”-forward products (typically leave-on masks, gels, and essence/serum formulas) commonly place it in the 0.5–2% range, with high-strength consumer-available formulations reaching ~5% when the extract is a primary featured ingredient and/or when the supplier material is less diluted. There is no specific EU/FDA maximum for this cosmetic plant extract; practical upper limits are driven by odor/color, stability, and irritation/sensitization management rather than regulation.

Pyrus Malus Fruit Extract

Pyrus Malus (apple) fruit extract is typically used at low concentrations as an antioxidant/conditioning botanical, but it contains naturally occurring fruit acids (e.g., malic acid) and polyphenols that can sting or provoke irritation on compromised barriers. Clinical patch-test experience with botanical extracts shows a nontrivial rate of irritant reactions in sensitive/eczema-prone populations, especially when combined with other actives in a full routine. Given variable composition and the higher-risk profile of plant extracts on reactive skin, a mild irritancy score is the safest clinically aligned choice. Safety Notes: In mass-market lotions, toners, cleansers, and shampoos, Pyrus Malus (Apple) Fruit Extract is commonly used as a label-claim botanical at very low levels (~0.001–0.1%), often as part of a blended extract system. Mid-range leave-on moisturizers/serums and rinse-off exfoliating/brightening products more typically sit around ~0.1–2%. High-strength consumer products marketed as “fruit/enzyme” masks, peel-style exfoliants, and botanical concentrates can reach ~5–10% of the commercial extract (with the practical ceiling driven by supplier solvent/glycerin load, color/odor, and stability), and there are no specific FDA/EU maximum-use limits for this INCI beyond general safety substantiation.

Quaternium-15

Quaternium-15 is a formaldehyde-releasing preservative used at low concentrations, but it is a well-documented cause of allergic contact dermatitis on patch testing and can also sting/irritate compromised skin. In sensitive populations (eczema, barrier disruption), the sensitization risk and potential for significant flare-ups are high enough that I treat it as a very high irritancy ingredient from a patient-safety standpoint. Safety Notes: In legacy consumer cosmetics and personal care products (e.g., shampoos, liquid soaps, lotions, and some makeup) Quaternium-15 has been observed at low use levels around ~0.05% when used as part of a broader preservative system, with many formulations historically clustering near 0.1%. The highest over-the-counter use levels seen in commercial products are around 0.2%, which aligns with the typical maximum permitted concentration referenced in EU cosmetic regulation for this preservative; it was used in both rinse-off and leave-on products, though its market presence has declined substantially due to sensitization concerns.

Quaternium-18 Hectorite

Quaternium-18 Hectorite is an organoclay rheology modifier/suspending agent used at low levels (typically ~0.5–3%) to thicken and stabilize emulsions and makeup. As an insoluble clay treated with a quaternary ammonium compound, it is generally well tolerated in patch testing and real-world use, with irritation more likely from the overall formula (e.g., solvents, surfactants) than from the clay itself. Rare mechanical dryness or reactivity can occur in highly compromised eczema skin, but its intrinsic irritancy is low, supporting a very gentle score. Safety Notes: Quaternium-18 Hectorite is an organoclay rheology modifier/suspending agent used at very low levels (~0.05–0.3%) in leave-on creams/lotions and some rinse-off cleansers to stabilize oils, pigments, and insoluble actives. In high-oil, anhydrous or silicone-rich systems (e.g., foundations/primers, balm/ointment textures, certain hair styling and specialty skincare suspensions) commercial products and supplier formulating guidance commonly reach ~1–3%, with upper-end consumer-available thickened/suspension systems observed up to ~5% for maximum structure and anti-settling performance.

Quercetin

Quercetin is a plant-derived flavonoid used as an antioxidant/anti-inflammatory active in topical products, typically at low concentrations (about 0.1–1%), but it has limited robust human irritancy data and can be delivered in solvent systems that increase stinging. While many users tolerate it, botanical polyphenols do produce occasional irritation or contact reactions in reactive/eczema-prone skin, so I score it as mild to reflect nonzero risk and prioritize patient safety. Safety Notes: In commercial skincare, quercetin is most often used in leave-on antioxidant/anti-pollution serums and creams at very low levels (~0.001–0.05%) due to solubility, color/odor, and oxidation/stability constraints, with some products using solubilized or encapsulated forms around 0.1–0.5%. High-strength consumer-available “flavonoid/antioxidant concentrate” serums and booster drops occasionally reach ~1–2% quercetin (typically with solvent systems, glycols, cyclodextrin/encapsulation, and strong stabilization), while rinse-off products generally sit at the lower end because of limited contact time and cost.

Quercus Alba Bark Extract

Quercus alba (white oak) bark extract is a tannin-rich botanical astringent used at low percentages for oil control, pore feel, and soothing claims. While not a classic strong irritant, tannins and complex plant constituents can provoke stinging/dryness on compromised barriers and have documented potential for irritant or allergic contact dermatitis in sensitive individuals. Given the variability of botanical extracts and real-world eczema risk, it warrants a mild irritancy score rather than being treated as inherently “gentle.” Safety Notes: In commercial skincare, Quercus alba (white oak) bark extract is most often used as an astringent/soothing botanical at very low levels (trace to ~0.1%) in toners, lotions, aftershaves, and cleansers, where it functions as part of a broader botanical blend. Higher-strength consumer products such as targeted pore-refining/anti-blemish serums, post-shave treatments, and some deodorant/foot-care or scalp tonics can use single botanical extracts at ~1–5% (typically as the supplier’s extract solution), with practical upper limits driven by tannin-associated color/odor, potential irritation, and formula stability; rinse-off products can sometimes sit toward the upper end due to shorter contact time. No specific EU/FDA maximum is set for this botanical extract, so observed market use is primarily constrained by tolerability and aesthetic/formulation considerations.

Raffinose

Raffinose is a non-ionic oligosaccharide used mainly as a humectant/skin-protective sugar at low percentages, and sugars of this class are generally well tolerated in leave-on products. It is not a pH-dependent active and lacks the protein-reactive chemistry typical of common irritants, so irritation risk is low, though very reactive or eczematous skin can still sting with high-osmolality humectant systems or compromised barriers. Given its typical use and low sensitization profile, it fits a very gentle (but not inert) rating. Safety Notes: In commercial skincare, raffinose is most often used as a minor humectant/prebiotic-style sugar or as part of a multi-sugar osmolyte blend, where it commonly appears at trace-to-low levels (~0.01–0.3%) in leave-on serums/creams and occasionally rinse-off cleansers. Higher-strength consumer products (especially “prebiotic/moisture complex” leave-on formulas and some sheet-mask essences) can push total raffinose to around 1–3%, with the upper end (~5%) observed in specialized OTC hydration/barrier-support formulations where tackiness and microbial control are managed with system design. There are no specific FDA/EU cosmetic concentration caps for raffinose; practical limits are driven by sensory/stability (stickiness, crystallization risk at high solids) and preservative robustness.

Raphanus Sativus Root Extract

Raphanus Sativus (radish) root extract is typically used at low concentrations as an antioxidant/skin-conditioning botanical, and most users tolerate it well. However, botanical extracts contain multiple bioactive constituents and can trigger irritation or allergic contact reactions in a small but meaningful subset of sensitive/eczema-prone patients, especially in compromised skin barriers. Given that risk profile and the lack of strong evidence that it is universally inert, I rate it as gentle but not risk-free. Safety Notes: In commercial skincare, Raphanus Sativus (radish) root extract is most often used as a minor botanical/skin-conditioning component or part of a preservative blend, where it commonly appears around 0.01–0.5% (leave-on and rinse-off). Higher levels are seen in “natural/clean” formulas and some extract-forward serums/masks where the brand loads botanical extracts, with observed consumer-available products reaching ~1–5% depending on extract type and solvent system. The upper end is constrained mainly by sensorial impact, color/odor, and overall formula stability/compatibility rather than a specific global regulatory maximum for the extract itself.

Raphanus Sativus Seed Oil

Raphanus Sativus (radish) seed oil is a lipid emollient used typically at a few percent up to full-oil phases in moisturizers, and as a class, cosmetic plant seed oils have low irritancy in standard patch testing when properly refined. The primary risk is idiosyncratic allergy or irritation in highly reactive eczema patients (less common than with fragranced/essential oils), so I score it as very gentle but not fully inert. Safety Notes: In commercial skincare and haircare, Raphanus Sativus (Radish) Seed Oil is commonly used as a lightweight emollient/slip agent and can appear at low levels (~0.1–1%) in lotions, creams, and cleansers where it functions as part of the oil phase. It is also sold directly to consumers as a single-ingredient facial/body oil or as a primary carrier oil in blends, where it can reach 50–100% in leave-on products. There are no specific EU/FDA maximum concentration limits for this cosmetic ingredient; practical upper use is governed by sensory profile, oxidation management, and formula type (leave-on vs rinse-off).

Raspberry Ketone

Raspberry ketone (4-(4-hydroxyphenyl)-2-butanone) is primarily used as a fragrance/flavor component and can also appear in “slimming” or “natural” claims products, typically at low percentages but often alongside other sensitizing fragrance materials. As an aromatic ketone/phenolic compound, it carries a meaningful risk of irritation and allergic contact dermatitis in reactive or eczematous skin, and fragrance-type ingredients are overrepresented in patch-test reactions. Given the severe-sensitivity population and the unpredictability of fragrance allergen cross-reactivity, I score it as a notable risk requiring careful avoidance or patch testing. Safety Notes: In mainstream consumer skincare, raspberry ketone is most often used as a low-level fragrance/marketing botanical-active at trace levels around 0.001–0.05%, especially in leave-on body lotions and anti-cellulite/firming products where it is typically solubilized in fragrance or glycols. Higher-strength OTC specialty ‘slimming/firming’ body serums and creams have been marketed around ~0.5–2% raspberry ketone; above ~2% is uncommon in cosmetics due to strong odor, solubility/compatibility limits, and increased irritation/sensitization risk. This range reflects observed consumer-available leave-on products; rinse-off products generally sit toward the lower end because of brief contact time and cost/odor constraints.

Rehmannia Chinensis Root Extract

Rehmannia Chinensis Root Extract is a botanical extract used mainly for soothing/antioxidant claims, typically at low concentrations (often well under 1–2%). While not a known high-irritancy active, botanical extracts have meaningful variability and can trigger irritant or allergic contact dermatitis in sensitive/eczema-prone populations due to complex phytochemical content and potential contaminants, so I rate it as mild rather than “gentle.” In real-world routines with multiple botanicals and preservatives, cumulative reactivity is plausible, warranting cautious placement at 0.4. Safety Notes: In commercial skincare, Rehmannia Chinensis Root Extract (a TCM botanical) is most often used as a low-level supporting extract in multi-botanical soothing/anti-aging formulas, commonly in the ~0.001–0.1% range (leave-on toners, emulsions, and serums), especially when supplied as a glycerin/butanediol-based extract. Higher-strength consumer-available products marketed as “herbal/hanbang concentrates” or mask/ampoule-style products can reach ~1–5% of the extract solution, with practical upper limits driven by odor/color, stability, and tack; rinse-off cleansers typically sit toward the low end due to brief contact time. There are no specific FDA/EU maximum limits for this INCI, so observed market use is primarily constrained by formulation aesthetics and supplier extract potency.

Rehmannia Glutinosa Root Extract

Rehmannia glutinosa root extract is a botanical skin-conditioning/soothing ingredient typically used at low concentrations (often well under 1–2%) and is generally well-tolerated in leave-on formulas. However, as a plant extract it contains multiple bioactive compounds and can trigger irritant or allergic contact dermatitis in a minority of highly reactive or eczema-prone patients, especially in compromised skin or complex multi-extract blends. Given the limited standardized patch-test data compared with core inert ingredients and the real-world variability of extract purity/solvents, a gentle-but-not-inert score is the safest clinically aligned assessment. Safety Notes: In commercial skincare (especially K-beauty/Asian herbal and ‘hanbang’ positioning), Rehmannia Glutinosa Root Extract is frequently used as a supporting botanical at very low levels (≈0.001–0.1%) in toners, emulsions, and multi-extract blends where it primarily serves a marketing/soothing story. Higher-strength consumer products such as concentrated serums/ampoules and herbal concentrate creams can reach ~1–5% when the extract is a primary featured active and the system is designed to manage color/odor and stability; rinse-off cleansers typically sit toward the low end due to cost and wash-off contact time. No specific EU/FDA maximum is set for this botanical extract, so observed market limits are driven mainly by sensorial constraints, raw material potency/solids, and stability rather than regulation.

Resveratrol

Resveratrol is an antioxidant/anti-inflammatory polyphenol typically used around ~0.1–1% in leave-on serums, but it can be irritating in reactive or eczematous skin—especially because it’s often formulated in penetration-enhancing solvents (e.g., propanediol/ethoxydiglycol) that increase stinging risk. Human experience and patch/consumer use data suggest most tolerate it, yet a meaningful minority report burning/redness or dermatitis, so it is best categorized as mild rather than “gentle” for compromised barriers. Safety Notes: In consumer skincare, resveratrol is most often used in leave-on serums/creams at very low levels (around 0.001–0.05%) due to cost, oxidation/light sensitivity, and frequent pairing with synergists (e.g., ferulic acid, vitamin E) where only small amounts are needed. Mainstream antioxidant serums commonly sit around ~0.1–1%, while a small number of high-strength, direct-to-consumer “booster”/serum products reach about 2–3% (typically anhydrous, encapsulated, or otherwise stabilized to manage solubility and stability). Rinse-off products generally fall toward the lower end because short contact time reduces the incentive to formulate at higher levels.

Retinal

Retinal (retinaldehyde) is a potent vitamin A derivative used typically around ~0.05–0.1% in cosmetics and is closer to retinoic acid in conversion steps than retinol, which increases the likelihood of erythema, burning, peeling, and barrier disruption—especially during initiation. Clinical experience and comparative tolerability data for topical retinoids show meaningful irritation is common in sensitive and eczematous populations even at standard concentrations, and cumulative irritation is amplified when paired with acids, benzoyl peroxide, or frequent cleansing. Given its active potency and predictable retinoid dermatitis risk in compromised skin, it warrants a high irritancy score with careful introduction and buffering. Safety Notes: In consumer leave-on skincare, retinal (retinaldehyde) is commonly marketed at low levels around 0.01% and can be found as low as ~0.005% in sensitive-skin or “starter” serums/creams, sometimes due to dilution from encapsulated/delivery-complex actives. High-strength OTC products marketed specifically as intensive retinal treatments are observed up to ~0.2% retinal; above this is uncommon in mass-market retail due to irritation risk and stability/oxidation constraints. Retinal is essentially used in leave-on products (serums/creams) rather than rinse-off formats because contact time is required for efficacy.

Retinol

MVP Approved - Retinol is a potent vitamin A derivative widely used for its proven anti-aging and acne-fighting actions while also improving overall skin texture; however, its benefits can come at the price of moderate irritation such as dryness and peeling during initial use.

Retinyl Acetate

Retinyl acetate is a vitamin A ester used in cosmetics typically around ~0.05–1% as a gentler retinoid precursor, but it can still convert (directly or via retinol) to active retinoid forms that increase epidermal turnover. Clinical experience and patch/usage testing show retinoid esters are generally less irritating than retinol/retinal but can still cause dryness, stinging, and eczematous flares in sensitive or compromised skin, especially when combined with other actives. Given the real-world cumulative irritation risk in routines and the need for gradual introduction in reactive populations, it warrants a notable-active score. Safety Notes: In commercial skincare, retinyl acetate is often used at trace levels (~0.0001–0.01%) in mass-market moisturizers, sunscreens, and “vitamin A” antioxidant blends where it functions more as a label/maintenance ingredient than a primary active. Higher-strength OTC leave-on serums and night creams marketed as retinoid treatments commonly fall around ~0.05–0.2%, with a small number of consumer-available specialty formulas approaching ~0.5% when positioned as a stronger vitamin A ester alternative (still generally lower-irritancy than retinoic acid). Retinyl acetate is uncommon at high levels in rinse-off products due to limited contact time and the need to control photostability/oxidation, so the observed upper end is primarily leave-on.