Skincare Ingredients

Myristic Acid

Myristic acid is a saturated fatty acid primarily used as a surfactant/cleansing and opacifying agent (often via soaps/salts) and can be present at meaningful levels in cleansers and bar soaps. While not a classic high-risk allergen, fatty-acid–based surfactants and soaps can disrupt the stratum corneum and increase transepidermal water loss, leading to stinging, dryness, and eczema flares—especially with frequent use or high-pH formulations. In sensitive or eczematous skin, the barrier-disruptive potential justifies a mild irritancy rating for patient safety. Safety Notes: In commercial skincare, myristic acid is often a minor co-emollient/co-surfactant or soap-structuring fatty acid in leave-on creams/lotions and some cleansers, where it can appear at trace-to-low levels (~0.05–1%). The highest consumer-available levels are found in high-foaming rinse-off facial cleansers and “soap-based” cleansing creams/bars (often paired with lauric/palmitic/stearic acids and neutralized with KOH/NaOH), where myristic acid can be a major fatty-acid feedstock reaching ~10–25% of the formula. Leave-on products rarely approach the upper end due to waxy feel and higher comedogenic/irritation potential; the upper range is mainly rinse-off.

Myristoyl Hexapeptide-16

Myristoyl Hexapeptide-16 is a lipidated signaling peptide used in anti-aging/firming products at low concentrations (typically well under 1%), and peptides as a class are generally well-tolerated in patch testing with low irritancy. The attached myristoyl (fatty) chain can very occasionally contribute to stinging or follicular intolerance in highly reactive or acne-prone users, but true irritation is uncommon at cosmetic use levels, supporting a very gentle score. Safety Notes: In commercial leave-on skincare (serums, eye creams, anti-aging moisturizers), Myristoyl Hexapeptide-16 is typically used at very low levels as a signal/lipofilic peptide, with many multi-peptide formulas dosing it around 0.0005–0.005% to manage cost and solubility while still supporting marketing/claims. Higher-strength consumer-available “peptide concentrate” serums and ampoules occasionally push toward ~0.02–0.05% as a standalone or lead peptide, which is near the upper practical end before stability/solubilization challenges and diminishing returns become limiting. It is overwhelmingly a leave-on ingredient; rinse-off uses are uncommon and, when present, tend to sit at the low end due to limited contact time.

Myristoyl Nonapeptide-3

Myristoyl Nonapeptide-3 is a lipopeptide used in anti-aging products, typically at low concentrations (generally well under 0.1–0.5%), and peptides as a class are usually well-tolerated in controlled use. However, the myristoyl (fatty-acyl) modification can increase skin interaction and, in highly reactive or eczema-prone patients, lipopeptides can occasionally sting or trigger irritation even when not classic sensitizers. Given limited large-scale irritation datasets specific to this exact peptide and the need to err toward patient safety, I rate it as gentle with low but non-zero irritation potential. Safety Notes: In consumer leave-on anti-aging/firming serums and eye creams, Myristoyl Nonapeptide-3 is typically used at very low levels consistent with peptide supplier guidance and market INCI practices (often ~0.001–0.01% active), with the lowest observed commercial uses around 0.0005% in multi-peptide blends. High-strength OTC formulations (peptide-focused serums/ampoules marketed for intensive use) are observed up to about 0.05% as an individual peptide active or as part of concentrated peptide complexes, above which cost, solubility, and diminishing returns generally limit real-world use. This ingredient is predominantly found in leave-on products; rinse-off applications are uncommon and generally sit at the low end due to short contact time.

Myristoyl Pentapeptide-17

Myristoyl Pentapeptide-17 is a lipidated signal peptide primarily used in lash/brow and cosmetic serums at low concentrations, and peptides of this class are generally well-tolerated with low rates of irritant reactions in routine use. The myristoyl (fatty acyl) modification can very occasionally contribute to stinging or follicular irritation in highly reactive or eczematous skin, but it is not a pH-dependent active and lacks the irritancy profile of acids, retinoids, or strong preservatives. Given typical leave-on use and sensitive-skin safety considerations, it fits best as very gentle rather than inert. Safety Notes: In consumer lash/brow serums and eye-area leave-on products, Myristoyl Pentapeptide-17 is commonly used at very low active levels (often ~0.0005–0.01%) because it is typically supplied as a dilute solution and is effective at low dosing; the lowest market observations are around 0.0001% in multi-peptide blends and budget formulas. High-strength, consumer-available lash/brow serums that position around “maximum peptide” dosing can reach ~0.05–0.10% active, which is near the practical upper end for solubility, cost, and sensory/stability constraints in leave-on aqueous/hydroalcoholic systems. It is rarely used meaningfully in rinse-off formats; the observed range is primarily for leave-on lash/brow and periocular products.

Myristyl Alcohol

Myristyl alcohol is a long-chain fatty alcohol used as an emollient/thickener (often ~0.5–5%) and is generally less irritating than short-chain alcohols, but it is not universally “non-irritating.” In patch testing and real-world use, fatty alcohols can trigger irritant or eczema flares in a reactive minority—especially on compromised skin—so I rate it as mild risk rather than inherently gentle. Safety Notes: In commercial skincare and haircare, myristyl alcohol is commonly used at very low levels (~0.05–0.5%) as a co-emollient/viscosity builder in lotions, cleansers, and conditioners, especially when paired with other fatty alcohols. Higher levels (5–15%) are seen in richer creams, balms, and conditioning products as part of the fatty-alcohol structuring system; the upper end (~20–25%) occurs in anhydrous sticks/balms and high-wax/fatty-alcohol bases sold OTC where myristyl alcohol functions as a primary structurant and slip agent. No specific EU/FDA concentration cap applies for this cosmetic ingredient; practical limits are driven by texture, melting profile, and compatibility (leave-on products tend to use higher levels than rinse-off).

Myristyl Glucoside

Myristyl glucoside is a nonionic alkyl polyglucoside surfactant/emulsifier typically used at low-to-moderate levels in cleansers and emulsions, where it is generally well tolerated compared with harsher anionic surfactants. However, as a cleansing surfactant it can still contribute to barrier lipid disruption and cumulative irritation, especially in eczema-prone or highly reactive skin and in rinse-off products used frequently. Patch-test and clinical experience place it in the generally low-irritant category, but not inert, so a gentle-risk score is appropriate. Safety Notes: Myristyl glucoside is used in consumer skincare primarily as a nonionic alkyl polyglucoside surfactant/solubilizer and mild emulsifying/co-surfactant, with low-end use around 0.1–0.5% in leave-on creams/lotions and micellar/cleansing waters to aid solubilization and sensorial feel. In rinse-off facial/body cleansers and shampoo-type washes it is commonly used at ~1–5% as part of the primary surfactant system, and high-strength consumer “minimal ingredient” cleanser concentrates can reach ~8–10% when it serves as a major/primary surfactant. There is no specific EU/FDA maximum for this ingredient; practical upper limits are driven by viscosity, clarity, foam/mildness balance, and irritation potential in leave-on formats.

Myristyl Myristate

Myristyl myristate is a fatty ester emollient/wax used to improve slip and texture, typically at a few percent up to ~10% in creams and makeup. It is not a common primary irritant or sensitizer in patch-testing data, but in very reactive or eczematous skin it can occasionally contribute to discomfort or follicular congestion when layered with other occlusive lipids. Given its generally good tolerability yet non-zero risk in compromised skin, a gentle (not inert) score is appropriate. Safety Notes: In commercial products, myristyl myristate is commonly used at very low levels (~0.05–1%) as a slip agent/structuring emollient in lotions, sunscreens, and makeup where it supports skin feel without strongly affecting viscosity. In richer leave-on creams, balms, pomades, and stick products it is used at much higher levels (typically 5–20%), and high-wax anhydrous sticks/balms and heavy emollient body products available OTC can reach about 25% as part of the lipid/structuring phase. It is not specifically concentration-restricted in major cosmetic regulations, with practical upper limits driven by texture, melting point, and potential for increased comedogenic feel in leave-on facial products.

Myristyl Nicotinate

Myristyl nicotinate is a nicotinic acid (niacin) ester used as a rubefacient/vasodilating skin-conditioning agent in topical products, typically at low percentages but specifically to induce increased blood flow and a warming/flushing effect. Clinically, nicotinate esters are well known to cause transient erythema, stinging, and burning—effects that are amplified in eczema-prone or barrier-impaired skin and can be mistaken for “irritation” because they are irritation by mechanism. Given its intentional vasodilatory activity and frequent reports of noticeable warmth/redness even at typical cosmetic use levels, I score it high for irritancy risk in sensitive populations. Safety Notes: Myristyl nicotinate is primarily used as a rubefacient/microcirculation-boosting nicotinic acid ester in leave-on body/leg “warming,” anti-cellulite, and massage products, where it is often present at very low levels (~0.01–0.1%) to provide a mild sensory effect while limiting flushing. In higher-intensity OTC slimming/firming and heat-activating formulations, concentrations commonly move into the 0.5–2% range, with a small number of consumer-available specialty products/formula concepts reaching about 5% to deliver a pronounced warming/tingling effect. Use above this level is uncommon in mass-market skincare due to irritation/flush potential and diminishing formulation practicality; rinse-off products typically use lower levels than leave-on products because the sensory benefit is reduced by short contact time.

Myrtus Communis Extract

Myrtus communis (myrtle) extract is a botanical antioxidant/astringent used at low concentrations, but it contains aromatic compounds (e.g., terpenes/phenolics) that are documented triggers for irritant and occasional allergic contact dermatitis in reactive and eczematous skin. In real-world routines it can add cumulative irritation—especially when layered with acids, retinoids, or compromised barrier states—so I score it as moderate and patch-test advisable for sensitive populations. Safety Notes: In mass-market and prestige leave-on products (toners, emulsions, serums) Myrtus communis extract is frequently used as a supporting botanical at very low levels (often ~0.001–0.1%) for soothing/antioxidant or sebum-support positioning, especially when supplied as a concentrated extract standardized in a carrier. Higher-strength consumer-available products (botanical “active” serums/ampoules, acne/oily-skin concentrates, and some rinse-off masks/cleansers) can reach ~1–5% when the supplier material is a typical glycerin/propylene glycol/water extract or similar, with practical upper limits driven by odor/color, potential sensitization, and formula stability rather than explicit regulatory caps.

Nannochloropsis Oculata Extract

Nannochloropsis oculata extract is a microalgae-derived skin-conditioning/antioxidant ingredient typically used at low concentrations in leave-on products, and it is not a classic primary irritant like acids, retinoids, or surfactants. However, as a complex botanical/algal extract containing multiple bioactive molecules (proteins, pigments, lipids), it carries a small but real risk of irritation or allergic-type reactivity in highly sensitized or eczema-prone patients. Given limited robust clinical irritation datasets compared with more standardized actives, I rate it as generally gentle but not inert. Safety Notes: In mass-market leave-on products (serums, creams, eye products), Nannochloropsis oculata extract is often used as a minor “marine/algae” supporting active at ~0.0005–0.05% due to typical supplier dilutions (e.g., extract-in-glycerin/butanediol) and cost/odor/color constraints. Mid-range formulations commonly land around ~0.1–1% when the extract is a marketed feature, especially in anti-aging/firming leave-on products. The upper end (~3–5%) is observed in consumer-available “high-algae” gels/ampoules/masks and some rinse-off cleansers where higher loading is feasible, noting that at very high levels the INCI may represent a diluted extract rather than 100% dry biomass.

Narcissus Poeticus Flower Wax

Narcissus Poeticus Flower Wax is a botanical wax used mainly as an emollient/texture agent at low concentrations, but it is a plant-derived aromatic material that can contain trace fragrance-like constituents. In sensitive and eczema-prone patients, botanical extracts/waxes have a meaningful risk of irritation or allergic contact dermatitis compared with inert waxes (e.g., petrolatum), so I score it as moderate to prioritize patient safety and patch testing. Safety Notes: In commercial skincare, Narcissus Poeticus Flower Wax is most often used as a minor structuring/emollient wax or sensorial modifier within complex botanical blends, where it can appear at very low levels (down to ~0.0005–0.01%) especially in leave-on serums/creams marketed with rare florals. The highest consumer-available levels are seen in anhydrous leave-on products (balms, solid perfumes, salves, high-wax lip/skin sticks) and some rich creams where it can function as a primary wax structurant, reaching about 1–5% in niche/high-strength “floral wax” positioning; rinse-off products typically sit at the low end due to cost and limited functional need.

Naringenin

Naringenin is a citrus-derived flavonoid used as an antioxidant/anti-inflammatory active, typically at low concentrations (often well under 1%) in leave-on products. While generally well-tolerated, plant polyphenols can still trigger stinging or irritant reactions in compromised barriers and have a non-zero risk of delayed sensitivity in highly reactive eczema patients, especially given botanical-source variability. Scoring it as mild reflects cautious clinical practice: low expected irritation in most users but meaningful risk in the most sensitive populations. Safety Notes: In commercial skincare, naringenin is most often used as a minor flavonoid antioxidant/soothing component either as a trace constituent of citrus/botanical extracts or as a labeled active at very low levels, commonly around 0.0001–0.05% in leave-on creams/serums. Dedicated “pure flavonoid”/brightening or antioxidant booster products and some high-strength, consumer-available specialty serums (often solubilized or encapsulated due to low water solubility) have been observed up to about 1–2% in leave-on formats; rinse-off products are typically lower because of short contact time.

Nelumbo Nucifera Flower Extract

Nelumbo nucifera (lotus) flower extract is primarily used as an antioxidant/soothing botanical at low concentrations, but as a complex plant extract it contains multiple potential sensitizing constituents (e.g., polyphenols and trace fragrance-like compounds depending on extraction) that can trigger irritation or allergic contact dermatitis in reactive or eczematous patients. Human patch-test and dermatology surveillance data for lotus specifically are limited compared with core emollients, so I do not classify it as “gentle” by default; in compromised skin the risk is meaningfully higher than inert bases. Given typical leave-on use and cumulative exposure alongside other actives, a mild irritancy score best matches patient-safety expectations. Safety Notes: In mass-market and prestige leave-on products (toners, emulsions, creams, sheet-mask essences), Nelumbo nucifera flower extract is often used as a botanical “label” component at very low levels (down to ~0.0001–0.01%), especially when supplied as a diluted extract in glycerin/propylene glycol and added late in the INCI list. More active-positioned botanical/“lotus” serums and mask concentrates sold OTC commonly use ~0.5–2% of the commercial extract, and the highest consumer-available formulas I’ve observed go up to ~5% (typically in leave-on essences/serums), with higher levels being limited mainly by odor/color, solubility, and overall botanical load rather than specific regulatory caps.

Neopentyl Glycol Dicaprylate/Dicaprate

Neopentyl Glycol Dicaprylate/Dicaprate is a low-polarity emollient ester used to improve slip and barrier feel, typically present at a few percent up to higher levels in moisturizers and makeup. As a large, non-volatile lipid ester it is generally non-stinging and shows low rates of irritation in standard use, but like other emollient esters it can still trigger mild irritation or follicular issues in a small subset of highly reactive or eczematous patients, especially under occlusion. Given sensitive-skin safety considerations, it fits best as very gentle rather than fully inert. Safety Notes: Neopentyl Glycol Dicaprylate/Dicaprate is a lightweight emollient/skin-conditioning ester used both as a minor slip/sensory modifier and as a primary emollient in anhydrous or low-water lipid phases. In mass-market leave-on lotions/serums it is often present at trace-to-low single digit levels (~0.1–5%) to improve spreadability and reduce greasiness, while higher-oil products (body oils, lip products, oil-based makeup/removers, balms, and water-resistant sunscreens) commonly use it around 10–25% as a key emollient. The upper end observed in consumer OTC products can reach ~30–35% where it functions as a major component of the oil phase; rinse-off products typically use lower levels due to cost and deposition needs.

Neopentyl Glycol Diethylhexanoate

Neopentyl Glycol Diethylhexanoate is a non-volatile emollient ester/slip agent typically used at a few percent up to ~10%+ in moisturizers and makeup, and it is not an active or pH-dependent ingredient. Available safety and patch-test data for similar fatty esters suggest low irritation and low sensitization potential, with reactions being uncommon but possible in highly reactive or eczema-prone skin when barrier function is compromised. Given its generally good tolerability but non-zero risk in severely sensitive populations, it fits best as “very gentle” rather than inert. Safety Notes: Neopentyl Glycol Diethylhexanoate is a lightweight emollient/solvent ester used to improve spread, reduce greasiness, and aid pigment/UV filter wetting; in many leave-on lotions, serums, sunscreens, and color cosmetics it appears at low supportive levels around ~0.1–2%. In richer leave-on creams, makeup (foundations/concealers), and some sunscreens it commonly sits in the ~3–15% band as part of the emollient phase. High-slip anhydrous products (facial oils, makeup primers, balm sticks, oil-based makeup removers) can push ester levels much higher, and I have observed consumer OTC formulas using this ester up to ~30–40% as a primary emollient; rinse-off products tend to remain at the low end due to wash-off and phase-structure needs.

N-Hydroxysuccinimide

N-Hydroxysuccinimide is used in topical brightening/anti-dark-circle products (often alongside peptides like palmitoyl tripeptide-1/tetrapeptide-7) typically around ~0.1–1%, where it functions as a reactive small molecule rather than an inert solvent. While not a classic high-irritancy active like exfoliating acids or retinoids, its chemistry and limited broad safety history in very compromised skin mean stinging or mild dermatitis can occur in reactive users, especially around the thin periocular area and in eczema-prone patients. Given the sensitive-skin context and the need to avoid underestimation, a mild irritancy score is the safest clinically aligned rating. Safety Notes: N-Hydroxysuccinimide is most commonly encountered in leave-on under-eye “dark circle”/de-puffing serums and creams (often paired with chrysin and peptides), where commercial formulas at the low end use trace-to-support levels around 0.01–0.1% to complement the blend. The majority of mainstream products cluster roughly ~0.1–0.5%, while a small number of high-strength consumer-available targeted eye treatments and boosters push total N-hydroxysuccinimide up to about 1–2% before sensorial/stability and irritation constraints become limiting. It is rarely used in rinse-off products, and when present it is typically at the low end due to short contact time and cost/benefit.

Niacin

Niacin (nicotinic acid, vitamin B3) is primarily used as a vitamin/skin-conditioning agent, but at typical cosmetic-use levels it can trigger vasodilatory flushing, stinging, and warmth—reactions that are more pronounced in rosacea-prone and barrier-impaired (eczema) skin. Patch testing and real-world reports show it is less predictable than niacinamide, with irritation more likely when combined with other actives or low-pH routines. Given sensitive-skin safety considerations and the potential for notable immediate reactivity, a moderate irritancy score is warranted. Safety Notes: In commercial skincare, niacin (nicotinic acid) is used at very low levels (~0.01–0.1%) in sensitive-skin moisturizers/serums to minimize flushing while supporting barrier and tone benefits, and it appears similarly low in many rinse-off cleansers. The upper end of OTC consumer products is typically capped around ~0.5–1.0% because higher levels significantly increase irritation/flushing risk and are uncommon outside professional or drug-type uses; most leave-on products marketed for efficacy cluster below this ceiling.

Niacinamide

MVP Approved - Niacinamide is widely recognized as a multifunctional skincare ingredient that helps fortify the skin barrier, regulate oil, address hyperpigmentation, and reduce redness.

Nicotiana Benthamiana Hexapeptide-40 Sh-Oligopeptide-1

This is a plant-produced recombinant EGF-like signaling peptide used at very low concentrations (typically ppm-level) for skin-repair/anti-aging claims, and such peptides are generally well tolerated with low direct irritancy in patch-test experience. However, as a bioactive growth-factor–type protein, it can occasionally provoke stinging or reactivity in highly compromised eczema skin, and the plant-expression context raises a small but non-zero risk of trace impurities triggering sensitivity. Given patient-safety prioritization for severely reactive populations, I rate it as gentle but not inert. Safety Notes: In commercial leave-on skincare, this plant-produced recombinant peptide blend (often supplied as a dilute solution and used as an “active” complex) is typically dosed at very low levels, with entry-level anti-aging serums/creams using around 0.00005–0.001% active to support marketing claims while maintaining stability and cost targets. Higher-strength consumer serums marketed as growth-factor/EGF-like or “bioactive peptide” formulas have been observed using up to ~0.05% active, which represents the upper end seen OTC before viscosity, stability, and cost become limiting. It is rarely used in rinse-off products, and when present there, levels generally sit at the low end due to short contact time.

Nigella Sativa Seed Oil

Nigella sativa (black seed) oil is an emollient plant oil typically used at low-to-moderate percentages, but it contains bioactive compounds (e.g., thymoquinone and volatile constituents) that can trigger irritation or allergic contact dermatitis in a minority of users, especially on eczematous or barrier-impaired skin. Clinical experience and patch-test reports suggest most tolerate it, yet reactive individuals can flare, so I rate it as mild rather than “gentle” for high-sensitivity populations and cumulative routines. Safety Notes: In commercial skincare, Nigella sativa (black seed/cumin) seed oil is often used at very low levels (~0.05–0.5%) as a supporting emollient/marketing botanical within complex creams, lotions, and cleansers, where odor, color, and oxidation control typically limit higher loading. Dedicated facial oils, balms, and anhydrous treatments commonly use ~5–30%, and the consumer market also includes single-ingredient black seed oil products sold as topical oils that are effectively 100% (leave-on). There are no specific EU/FDA maximum concentration limits for this cosmetic ingredient, so the practical upper bound is set by sensorial/stability considerations rather than regulation.

Nonapeptide-1

Nonapeptide-1 is a synthetic peptide used primarily as a skin-brightening agent at concentrations typically between 0.005-0.01%. Clinical studies and patch testing data demonstrate excellent tolerance with minimal irritation potential, as peptides of this size generally have low dermal reactivity and do not penetrate deeply enough to trigger significant inflammatory responses. While extremely rare sensitivities can occur with any peptide sequence, the molecular structure and typical formulation concentrations make this suitable for daily use in sensitive skin populations. Safety Notes: In commercial leave-on brightening/spot-correcting serums and creams, Nonapeptide-1 is commonly dosed at very low levels (often ~0.0005–0.005%) due to potency and typical supplier recommended use rates; the lowest observed levels in complex multi-peptide blends and mass-market brightening products can be around ~0.0001%. High-strength consumer-available targeted dark-spot serums and “peptide concentrate” products occasionally reach ~0.01% when used as a primary active, while rinse-off formats rarely use it or keep it at the very low end because of contact-time limitations and cost.

Nordihydroguaiaretic Acid

Nordihydroguaiaretic Acid (NDGA) is a potent polyphenolic antioxidant/anti-inflammatory used at low concentrations in topical formulas, but it is an active botanical-derived molecule rather than an inert excipient. Human patch-testing and case reports with NDGA-containing products (e.g., creosote bush derivatives) show that it can provoke irritant and occasional allergic contact dermatitis in reactive or barrier-impaired patients. Given its biologic activity and documented dermatitis potential, I score it as a notable irritant requiring cautious introduction and patch testing, especially in eczema-prone skin. Safety Notes: Nordihydroguaiaretic acid (NDGA) is an uncommon antioxidant/anti-inflammatory used mainly in niche OTC leave-on serums/creams and scalp products; in commercial INCI lists it is most often present at low, supportive levels around 0.01–0.1% due to solubility, odor/color, and irritation/sensitization considerations. High-strength consumer-available formulations marketed for oil-control/blemish or intensive antioxidant support have been observed up to ~1–2% (typically leave-on, often in hydroalcoholic/solubilized systems), while rinse-off use is rarer and generally kept at the low end because contact time is short and higher levels can increase irritation risk.

Nylon-12

Nylon-12 is an inert synthetic polymer powder used in cosmetics (often a few percent) for slip, oil absorption, and blurring, and it is generally non-reactive in standard patch-testing with very low rates of irritation. The main risk is mechanical/drying discomfort or occlusion-related exacerbation in highly compromised eczema skin rather than true chemical irritation or sensitization. Given its strong tolerability profile but acknowledging rare reactivity in severely barrier-impaired patients, it fits "exceptionally gentle" rather than completely inert. Safety Notes: Nylon-12 is used as a texturizing/soft-focus polymer powder and slip agent; in many leave-on skincare (lotions/serums/primers) it appears at low levels (~0.1–2%) to improve feel and reduce tack without visible powderiness. In oil-control and blurring products (primers, matte moisturizers, silicone gel creams, sunscreen primers) and some loose/pressed hybrid skincare-makeup items available OTC, total nylon-12 loading commonly rises to ~5–15% and can reach ~20–25% in very high-powder, strong-mattifying consumer formulas. Rinse-off use exists (e.g., cleansers) but typically stays low due to cost/need, while the highest levels are overwhelmingly in leave-on, powder-rich textures.

Nylon-12 Fluorescent Brightener 230 Salt

This is a specialty optical brightener associated with nylon powder systems used for visual effects; such fluorescent brighteners are typically used at very low concentrations but are not widely supported by robust facial leave-on safety/patch-test data in highly sensitive populations. While nylon-12 itself is generally low-irritant, the added brightener salt increases uncertainty for irritancy and potential sensitization, so I score it as mild risk to prioritize safety for reactive and eczema-prone skin. Safety Notes: In consumer cosmetics, fluorescent brighteners used for optical brightening/blue-violet correction are typically dosed at very low levels, commonly around 0.001–0.05%, especially in leave-on tone-up/brightening primers, foundations, and some body lotions where minimal staining and photostability are needed. Higher-strength OTC products marketed for “instant brightening” or stronger optical correction (often makeup-adjacent leave-on formats and some rinse-off cleansers) have been observed up to about 0.1–0.5%, with the upper end constrained by color shift, fluorescence intensity, potential fabric staining, and general formulation aesthetics rather than a specific global cosmetics maximum limit.

Nymphaea Alba Root Extract

Nymphaea alba (white water lily) root extract is typically used at low concentrations as a soothing/antioxidant botanical, but like many plant extracts it contains multiple bioactive compounds that can trigger irritant or allergic contact reactions in a minority of sensitive users. Patch-test and real-world dermatology experience show botanicals are a common source of unpredictable reactivity in eczema-prone skin, especially when used in leave-on formulas or layered routines. Given the variability in extract composition and the need to err on patient safety, I rate it as mild with occasional sensitivity possible. Safety Notes: In mass-market leave-on skincare, Nymphaea alba (water lily) root extract is commonly used as a minor soothing/antioxidant botanical at very low levels (often in the 0.0001–0.05% active extract range when supplied as a diluted glycerin/water extract and listed mid-to-late INCI). Higher levels are observed in “botanical-forward” serums, creams, masks, and some rinse-off cleansers where it is positioned as a hero plant extract, with practical upper use generally around ~0.5–2.0% for stability, odor/color control, and cost; OTC products rarely exceed this unless using a very dilute extract solution.

Nymphaea Tetragona Extract

Nymphaea tetragona (water lily) extract is typically used at low concentrations as a soothing/antioxidant botanical, and it is not considered an inherently irritant active like acids or retinoids. However, like many plant extracts it contains multiple bioactive compounds and carries a nontrivial risk of irritation or contact allergy in highly reactive or eczematous skin, especially in leave-on products. Given that botanical extracts are a common source of unpredictable sensitization despite “calming” marketing, a conservative gentle score is appropriate for patient safety. Safety Notes: Nymphaea tetragona (water lily) extract is most often used as a minor soothing/antioxidant botanical in leave-on toners, essences, gels, and creams, where it commonly appears at very low label-impact levels (~0.0005–0.1%) as part of multi-extract blends. Higher-strength consumer products (e.g., “single-hero” calming/brightening serums, ampoules, and mask/gel products) can reach ~1–5% when the manufacturer uses a defined extract solution or dry extract at meaningful loading, while rinse-off cleansers typically sit toward the lower end due to short contact time and cost/stability considerations.

Ocimum Basilicum Leaf Extract

Ocimum basilicum (basil) leaf extract is a botanical antioxidant/fragrance-adjacent ingredient whose composition often includes sensitizing aromatic constituents (e.g., linalool, eugenol/estragole depending on extract), making irritation/allergic contact dermatitis a clinically recognized risk in reactive skin. While typically used at low concentrations, leave-on exposure and cumulative use with other actives can meaningfully increase stinging, erythema, or eczema flares in sensitive populations. Given the variability of extracts and documented sensitization potential of basil-derived aromatics, I score it as a notable risk requiring caution and patch testing in eczema-prone users. Safety Notes: In mass-market leave-on and rinse-off skincare, Ocimum Basilicum (Basil) Leaf Extract is commonly used as a low-level “botanical support” ingredient (often within a broader plant-extract blend) at ~0.001–0.1%, driven by cost, color/odor control, and irritation/sensitization considerations. Higher-strength consumer products positioned as botanical/clarifying/antioxidant treatments and some natural/indie lines can use single extracts at ~1–5% (sometimes higher as a supplied dilution, but ~5% active extract in the finished product is a practical upper end for stability and sensorial limits). Rinse-off formulas can tolerate the upper portion of the range more easily, while leave-on products tend to cluster toward the lower end due to potential fragrance/allergen components and sensitization risk.

Octocrylene

Octocrylene is a UVB/short-UVA sunscreen filter typically used around 2–10% to stabilize other filters and improve water resistance. Clinical experience and patch-testing data show it is generally tolerated but can cause irritant and, more importantly, photoallergic/allergic contact dermatitis in a meaningful minority—especially in eczema-prone or highly reactive patients and when combined with other sensitizing sunscreen filters. Given the real-world frequency of reactions and the high-risk context of leave-on, sun-exposed use, I score it as a moderate irritancy/sensitization risk requiring patch testing in sensitive populations. Safety Notes: In commercial OTC sunscreens and SPF moisturizers, octocrylene is commonly present at low levels (~0.5–2%) as a photostabilizer for avobenzone and to boost SPF, including in daily leave-on facial products. The highest concentrations observed in consumer-available leave-on sunscreens in major markets reach the EU maximum of 10% (EU Cosmetics Regulation), especially in high-SPF water-resistant lotions/sprays; rinse-off products rarely use it and when they do it is typically at the low end.

Octyldodecanol

Octyldodecanol is a fatty alcohol emollient/solvent typically used at ~1–20% to improve slip and reduce transepidermal water loss; it is generally well tolerated and not an active with inherent irritant mechanisms. Human patch test data and broad cosmetic use suggest low irritation potential, but it can occasionally sting or contribute to irritation in highly compromised (eczema/post-procedure) skin due to its solvent/emollient nature and potential to increase penetration of co-applied ingredients. Given that rare reactivity is possible in very sensitive patients, I score it as gentle rather than exceptionally gentle. Safety Notes: In commercial skincare, octyldodecanol is commonly used at very low levels (~0.1–2%) as an emollient/solvent and pigment-wetting aid in lotions, sunscreens, and makeup-adjacent skincare, with rinse-off products often staying at the low end due to sensorial build. The highest consumer-available levels are found in anhydrous leave-on systems (oil-based balms, cleansing balms, barrier ointments, and certain stick products) where it can function as a primary emollient and carrier, reaching ~20–60% depending on the oil phase design. There is no specific FDA/EU concentration cap for octyldodecanol in cosmetics, so market limits are primarily sensorial, compatibility, and stability-driven.

Octyldodeceth-16

Octyldodeceth-16 is a nonionic ethoxylated fatty alcohol used as a solubilizer/emulsifier (often a few percent) in cleansers, micellar products, and lotions. As a class, ethoxylated surfactant-like ingredients are generally well tolerated but can sting or cause irritant dermatitis in compromised barriers (eczema, post-procedure), especially in leave-on formulas or when combined with other surfactants. It is not a common allergen, but given sensitive-skin and cumulative-routine considerations, it merits a gentle (not “very gentle”) score. Safety Notes: Octyldodeceth-16 is a nonionic ethoxylated surfactant/solubilizer and emulsifier commonly used at very low levels (~0.1–1%) in leave-on serums, sprays, and makeup to solubilize fragrances/oils or aid emulsification. In higher-surfactant systems (cleansers, micellar waters, makeup removers) and some anhydrous-to-aqueous cleansing oils/balms, commercial OTC formulas can push it into the mid-to-high single digits, with the upper end (~10–15%) seen in concentrated solubilizing or cleansing bases where it is a primary surfactant/emulsifier. No specific global OTC concentration cap is typically set for this ingredient beyond general cosmetic safety and impurity control, so market maxima are driven mainly by irritation/tolerability and stability constraints.