Skincare Ingredients

Betaine Salicylate

Betaine salicylate is a salicylate-based exfoliant (BHA alternative) typically used around 1–4% in leave-on products, delivering keratolytic activity that can disrupt the stratum corneum barrier. While often marketed as “gentler” than salicylic acid, clinical experience and irritant-pattern data for salicylates still show meaningful risk of stinging, dryness, and eczema flares, especially when layered with other actives or used on compromised skin. Given its active, barrier-altering mechanism and common routine-level cumulative irritation, it warrants careful introduction in sensitive populations. Safety Notes: In commercial consumer products, betaine salicylate is most often used as a BHA source at low levels (~0.1–1%) in gentle leave-on toners/essences and some rinse-off cleansers where it functions as a milder salicylate alternative. High-strength OTC formulations (primarily leave-on serums/peels marketed for acne/texture) commonly reach 4–6%, with a small number of consumer-available products observed up to about 8% (often positioned as “2% salicylic acid equivalent” and dependent on pH/vehicle). There is no specific global positive-list maximum for betaine salicylate itself, but salicylate safety/labeling expectations and irritation limits tend to constrain practical use, especially in leave-on products.

Beta-Sitosterol

Beta-sitosterol is a plant sterol used in low percentages as an emollient/skin-conditioning and barrier-support ingredient, and it is generally well-tolerated with a low rate of irritant reactions in cosmetic use. Patch-test and clinical experience suggest irritation is uncommon, but because it is typically plant-derived and can be present alongside other botanicals, rare reactions can occur in highly reactive or eczema-prone patients. Given its overall safety profile yet non-zero risk in sensitized populations, it fits best as very gentle rather than inert. Safety Notes: In commercial skincare, beta-sitosterol is most often used as a minor component of botanical lipid fractions (e.g., shea/avocado/soy unsaponifiables, phytosterol complexes) in leave-on creams/serums, where it can appear at very low incidental levels around 0.001–0.05%. Dedicated “phytosterol” barrier-repair and anti-redness products (including balms and rich emulsions) commonly run ~0.1–1% total added beta-sitosterol, with high-strength consumer-available concentrates and anhydrous balms reaching about 2% before solubility/texture and crystallization constraints typically limit further increases. Rinse-off products generally sit toward the low end because deposition is limited and sterols are used mainly for marketing/secondary skin-feel benefits.

Beta Vulgaris Root Extract

Beta Vulgaris (beet) root extract is primarily used as a humectant/antioxidant and skin-conditioning botanical, typically present at low concentrations (often <1–5%) in leave-on products. It is generally well tolerated, but as a complex plant extract it carries a small, non-zero risk of irritation or sensitization in highly reactive or eczema-prone individuals, especially when the barrier is compromised. Given that it is not an inert substance yet lacks strong irritant activity in typical cosmetic use, a gentle score is the safest clinically aligned assessment. Safety Notes: In commercial skincare, Beta vulgaris (beet) root extract is often used as a minor antioxidant/conditioning or “natural color/skin vitality” supporting botanical at trace-to-low levels, commonly around 0.001–0.1% in leave-on creams/serums and rinse-off cleansers where it is part of a broader botanical blend. Higher-strength consumer products (e.g., “beet” focused masks, ampoules, and natural/organic lines using single-hero botanical extracts or high-load aqueous glycerin extracts) can reach ~1–5%, with the upper end around ~10% when the supplied extract is a dilute carrier-based solution and is used primarily for marketing story, hue, and humectancy rather than as a regulated active; no specific EU/FDA cosmetic maximum applies, so practical limits are driven by stability, odor, and color impact.

Betula Alba Bark Extract

Betula Alba (birch) bark extract is a botanical antioxidant/soothing extract typically used at low concentrations, but it contains a complex mix of phenolics/terpenoids that can trigger irritation in reactive or eczematous skin despite “gentle” marketing. Clinical patch-test data for birch-derived botanicals show occasional irritant or allergic-type reactions (especially in atopic individuals and those with pollen/plant sensitivities), making it not reliably benign for severely sensitive skin. Given the variability in extract composition and real-world cumulative exposure in routines, I rate it as mild with a meaningful but not universal irritation risk. Safety Notes: In mass-market leave-on skincare (toners, serums, creams) Betula alba bark extract is commonly used as a minor botanical/soothing claim ingredient at very low levels (often supported by supplier-recommended use rates), with commercial products observed down to ~0.0005% when part of a multi-extract blend or at the tail of the INCI list. Higher-strength consumer-available “birch bark” calming/anti-redness formulas and ampoules sometimes dose the extract in the low single digits, with the upper end around ~5% for leave-on products before sensorial, color/odor, and stability constraints typically limit further increases; rinse-off products usually sit toward the lower end because of short contact time.

Betula Alba Juice

Betula alba (birch) juice is primarily used as a water-phase solvent/humectant substitute for water, typically at moderate-to-high levels, and is generally well tolerated in leave-on products. However, as a natural botanical sap it can contain trace proteins/salicylates and other plant constituents that have caused occasional irritation or contact allergy in reactive/atopic individuals, so I cannot score it as exceptionally gentle or inert. In sensitive-skin routines with multiple actives, its contribution to cumulative irritation is usually low but not negligible, supporting a conservative “gentle” rating. Safety Notes: In mass-market leave-on products (creams/serums/toners), Betula alba (birch) juice is often used as a minor botanical/skin-conditioning component or as part of a blend, with commercial listings commonly placing it around ~0.1–5% when not used as the primary aqueous phase. At the high end, some consumer-available toners/essences and mists are marketed as “birch juice” and use it as the main solvent instead of water, reaching ~70–98% depending on whether humectants/solubilizers/preservatives are included. Rinse-off cleansers typically sit toward the lower-to-mid end due to cost and because water remains the usual primary diluent.

Betula Alba Leaf Extract

Betula Alba (birch) leaf extract is a botanical soothing/antioxidant ingredient typically used at low concentrations, but plant extracts carry variable composition and can contain phenolics/salicylate-like constituents that provoke stinging or dermatitis in reactive or eczema-prone skin. Clinical patch-test data for birch leaf extract is limited and not strong enough to classify it as reliably "very gentle" across compromised barriers, so I rate it as mild irritation risk with occasional sensitivity possible. Safety Notes: In mass-market leave-on and rinse-off products, Betula Alba (birch) leaf extract is commonly used as a low-level botanical supporting ingredient, often at trace-to-low levels around 0.001–0.1% (especially when supplied as a diluted extract in a glycerin/propylene glycol/water carrier). Higher-strength consumer products marketed as botanical/soothing or “birch-focused” serums, toners, and masks can reach ~1–5% of the supplied extract, with practical upper limits driven by solvent load, odor/color, and stability rather than specific regulatory caps.

BHT

BHT (butylated hydroxytoluene) is an antioxidant used in cosmetics at low concentrations (typically ≤0.1%) to prevent rancidity. Clinical and patch-test data suggest it is generally well tolerated but can cause irritant or allergic contact dermatitis in a minority of users, especially those with compromised barriers (e.g., eczema). Given its documented sensitization potential despite low use levels, I rate it as mild rather than gentle for high-sensitivity populations. Safety Notes: In commercial cosmetics, BHT is used as an antioxidant to protect oils/fragrances and is often present at trace levels (~0.0001–0.01%) in mass-market leave-on creams, sunscreens, makeup, and fragranced products where it functions as a stabilizer. Many standard formulations sit around 0.01–0.1%, while the highest OTC consumer-available levels observed are in lipid-rich, oxidation-prone systems (e.g., anhydrous balms/sticks, certain hair oils/serums, and some long-wear color cosmetics) where brands may push toward ~0.2–0.5% for robustness. This range reflects real-world market use; BHT is typically similar in leave-on and rinse-off products, with the driver being oil load/oxidation risk rather than application type.

Bifida Ferment Filtrate

Bifida Ferment Filtrate is a postbiotic/ferment-derived skin-conditioning ingredient typically used at low single-digit percentages to support barrier function and reduce reactivity, and it is generally well-tolerated in sensitive-skin testing. However, as a biologically derived ferment, it can still trigger stinging or rare allergy in highly reactive or eczema-prone patients, especially when layered with other actives, so I do not score it as exceptionally inert. Safety Notes: In real-world commercial leave-on products (serums, essences, creams), Bifida Ferment Filtrate is often used at low supportive levels around ~0.1–1% to complement other humectants/actives, and it also appears at mid-levels (~2–10%) in barrier-focused formulas. The upper end is observed in consumer-available “ferment/biome” essence and ampoule-style products that feature Bifida Ferment Filtrate as a headline ingredient and can be formulated around ~15–20% (as supplied), whereas rinse-off cleansers typically sit at the low end due to short contact time. No specific FDA/EU maximum applies, so practical limits are driven by supplier standardization, odor/color, and stability/compatibility rather than regulation.

Bifida Ferment Lysate

Bifida Ferment Lysate is a probiotic-derived ferment used in leave-on skincare (commonly ~1–10%) for barrier support and soothing, and it is generally well-tolerated with low rates of stinging or erythema in routine use. However, as a biologically derived lysate/ferment (a complex mixture), it can still provoke irritation or rare sensitization in highly reactive or eczema-prone patients, especially when the skin barrier is compromised, so it is not scored as inert. Safety Notes: In commercial skincare, Bifida Ferment Lysate is often used at low supportive levels (~0.1–1%) in multi-ingredient leave-on serums/creams and in some rinse-off cleansers where it is primarily a marketing/skin-conditioning add. Many leave-on “microbiome/barrier” products and ampoules place it in the mid range (~1–10%), while a smaller set of consumer-available, fermentation-focused ampoules/essences use it as a primary base component, with observed INCI positioning consistent with very high levels (up to ~50%) without being prescription or professional-only.

Bioflavonoids

Bioflavonoids (a broad class of plant-derived polyphenols such as rutin/quercetin derivatives) are typically used at low concentrations for antioxidant/soothing support and are generally well tolerated on skin. However, because they are botanical extracts/actives with variable composition and occasional reports of contact dermatitis in highly reactive or eczema-prone patients, they carry a small but real irritation/sensitization risk. I score them as gentle rather than very gentle to reflect that variability and to prioritize safety in compromised skin. Safety Notes: In mass-market leave-on products (toners/serums/creams) “bioflavonoids” are often part of botanical or citrus extract systems and appear at very low labeling-relevant levels (~0.001–0.05%) where the extract is used mainly for antioxidant/soothing claims and color/odor constraints limit higher use. Dedicated antioxidant/brightening formulas and some consumer-available high-strength serums use enriched bioflavonoid complexes typically around 0.1–2%, with a small number of niche products pushing to ~3–5% total bioflavonoids in the active blend (higher levels are uncommon due to solubility, staining/yellowing, and increased irritation risk). Rinse-off products generally sit at the low end (often ≤0.1%) because of short contact time, while the highest concentrations are primarily seen in leave-on treatments.

Biosaccharide Gum-1

Biosaccharide Gum-1 is a high–molecular weight film-forming polysaccharide used mainly as a humectant/skin-soothing agent, typically at low concentrations (~0.1–1%). Clinical and post-market experience suggests very low irritancy and it is generally well tolerated even in reactive skin, though rare stinging or contact reactions can occur in highly compromised barriers, so it is not scored as completely inert. Safety Notes: In commercial skincare, Biosaccharide Gum-1 is commonly used as a soothing/hydrating film-former at low levels (~0.05–0.3%) in serums, toners, and moisturizers where it supports slip and comfort without noticeable tack. Many leave-on products cluster around ~0.2–1.0%, while higher-strength consumer-available gels/masks and barrier-repair concentrates can reach ~2–5% to deliver a more substantive protective film and sensory cushioning (often with increased viscosity/tack). Rinse-off products typically sit toward the lower end because deposition time is limited, whereas leave-on formats are where the upper end is most often observed.

Biotin

Biotin (vitamin B7) is typically used at low concentrations in topical “hair/skin/nail” products and functions as a supportive vitamin rather than an exfoliating or barrier-disrupting active. Clinical experience and patch-testing literature suggest it is generally well tolerated, with irritation or allergy being uncommon but possible in highly reactive individuals or when combined with other irritants in a formula. Given the need to account for sensitized/eczema-prone patients while recognizing its low inherent reactivity, it fits a very gentle profile. Safety Notes: In mass-market shampoos/conditioners, biotin is often included at very low “label claim” levels (commonly in the ~0.00001–0.01% range) primarily for marketing and because it is typically part of broader vitamin blends. Higher-strength OTC scalp serums, hair tonics, and leave-on treatments marketed for strengthening/thickening can reach ~0.1–0.5% biotin, with 0.5% representing the upper end seen in consumer-available products due to solubility, cost, and diminishing formulation practicality. Biotin appears in both rinse-off and leave-on products, with the highest levels more often found in leave-on scalp/hair treatments rather than rinse-off formats.

Biotin/Folic Acid/Cyanocobalamin/Niacinamide/Pantothenic Acid/Pyridoxine/Riboflavin/Thiamine/Yeast Polypeptides

This is a multi-vitamin/yeast polypeptide complex typically used at low concentrations for conditioning and barrier support; most components are generally well-tolerated in leave-on products. However, niacinamide can cause stinging/flushing in reactive skin (especially at higher percentages or in low-pH routines), and yeast-derived polypeptides/vitamin B12 have a low but real risk of triggering irritation or hypersensitivity in eczema-prone individuals. Given the mixture and cumulative routine effects, it fits a gentle-but-not-inert profile. Safety Notes: This is a multi-component “B-vitamin complex + yeast peptides” blend typically supplied as a premix and used at very low levels in mass-market leave-on lotions/serums and shampoos (often ~0.0001–0.05% as a label-claim complex, driven by potent/colored vitamins like folic acid and cyanocobalamin and typical supplier recommended use levels). Higher-strength consumer leave-on formulations are usually constrained by niacinamide tolerability and stability, but market-available brightening/acne serums can push the overall complex upward by using a niacinamide-heavy premix or combining with additional niacinamide to reach ~2–6% total blend in finished product. Rinse-off products generally sit in the lower end due to cost and limited contact time, while the upper end is predominantly leave-on serums/ampoules marketed for “vitamin B complex” or “barrier/brightening” benefits.

Bisabolol

MVP Approved - Bisabolol is a naturally derived, chamomile-based ingredient celebrated for its soothing properties that calm irritation and help reduce skin redness, making it ideal for sensitive and reactive skin.

Bis-Diglyceryl Polyacyladipate-2

Bis-Diglyceryl Polyacyladipate-2 is an emollient/texture enhancer (synthetic lanolin-like ester) typically used at a few percent in lip products and creams to improve slip and occlusivity. As a large, non-volatile, non-acidic lipid ester, it has low inherent irritancy and is generally well-tolerated in patch testing, though very reactive eczema patients can occasionally experience occlusion-related stinging or intolerance. Given its common use level and low reactivity profile but acknowledging compromised-skin unpredictability, it fits best as very gentle rather than inert. Safety Notes: Bis-Diglyceryl Polyacyladipate-2 is a lanolin-like emollient/texture agent used at low levels (~0.2–2%) in leave-on skincare (creams/lotions/serums) to boost slip, reduce tack, and improve barrier feel. In real-world color cosmetics (lipsticks, lip balms/glosses, and some cream makeup) it is often a primary structuring emollient, commonly 5–20% and in high-slip/high-gloss consumer lip products reaching ~25–35%. It is generally not a driver ingredient in rinse-off formats, where use levels tend to remain low due to cost and limited deposition benefit.

Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine

Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine (Bemotrizinol/Tinosorb S) is an oil-soluble, photostable UV filter typically used around 1–10% in sunscreens and is generally non-sensitizing with low irritation rates in patch testing. It is a large, poorly skin-penetrating molecule, which limits sting and inflammatory potential even in sensitive users. Mild irritation can still occur in highly reactive or barrier-compromised skin (often driven by the overall sunscreen vehicle rather than the filter), so it is best classified as very gentle rather than inert. Safety Notes: Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine (BEMT/Tinosorb S) is used almost exclusively in leave-on sun protection and daily moisturizers with SPF, where it may appear at low “supporting” levels around 0.1–1% in multi-filter formulas to boost UVA/UVB coverage and photostability. In high-protection OTC consumer sunscreens (especially EU/UK/Asia) it is commonly used in the ~2–7% range, with observed maximums reaching 10% in some high-SPF, broad-spectrum products. This aligns with EU cosmetic use limits where BEMT is permitted up to 10% in finished products; it is not relevant for rinse-off products and is generally uncommon/absent in US-only sunscreen formulas due to US OTC monograph constraints.

Bis-PEG-18 Methyl Ether Dimethyl Silane

Bis-PEG-18 Methyl Ether Dimethyl Silane is a PEG-modified silicone used mainly as a slip agent/emulsifier at low concentrations (typically ~0.5–5%) and is generally non-reactive with low patch-test irritancy in routine cosmetic use. In highly compromised skin, any surfactant-like emulsifier can very occasionally sting or contribute to barrier stress when layered with other actives, but this ingredient is far more often well tolerated than traditional detergents or strong preservatives. Given its overall inert silicone backbone yet acknowledging rare sensitivity in severely reactive patients, it fits best as very gentle rather than fully inert. Safety Notes: Bis-PEG-18 Methyl Ether Dimethyl Silane is a PEG-modified silicone surfassistant/emollient used mainly to improve slip, reduce tack, and aid dispersion/compatibility of silicones and oils in leave-on serums/primers as well as some rinse-off cleansers. In mass-market moisturizers and serums it is commonly present at low helper levels around 0.05–1%, while higher-slip, silicone-heavy consumer products (makeup primers, blurring/smoothing treatments, certain hair/skin conditioning concentrates) can use it as a more substantive component in the ~3–8% range. No specific EU/FDA maximum concentration limit is typically set for this INCI; practical upper use is constrained by aesthetics, cost, and overall surfactant/PEG-silicone balance for stability and irritation management (especially in leave-on products).

Bis-Phenylpropyl Dimethicone

Bis-Phenylpropyl Dimethicone is a high–molecular weight silicone emollient/skin-conditioning agent typically used at low to moderate levels to improve slip and reduce transepidermal water loss. Silicones of this type are generally non-reactive and show very low rates of irritation in patch testing, making them well-tolerated even in many sensitive-skin populations. Rare individual intolerance can occur (often related to the overall formula rather than the silicone itself), so it is best categorized as very gentle rather than completely inert. Safety Notes: In commercial leave-on skincare and hybrid skincare/makeup (primers, tinted moisturizers, blurring creams), Bis-Phenylpropyl Dimethicone is often used at very low levels (~0.05–0.3%) as a slip/feel modifier and gloss-enhancing silicone within larger emollient/silicone blends. Higher-use products such as silicone-rich smoothing primers, barrier creams, and facial oils/serums positioned for “silky” sensoriality can reach ~3–8% where it acts as a primary sensorial emollient and film former; rinse-off cleansers and wash-off masks typically sit at the low end due to dilution and deposition limits. No specific EU/FDA maximum applies for this INCI beyond general cosmetic safety obligations, so the observed upper end is driven mainly by aesthetics, compatibility, and viscosity rather than regulatory caps.

Bis(Tripeptide-1) Copper Acetate

Bis(Tripeptide-1) Copper Acetate is a copper-peptide signaling complex used at very low levels in anti-aging and barrier-support formulas, and peptides at these concentrations are generally well-tolerated in clinical use. However, copper salts/complexes can trigger stinging or irritation in a subset of reactive or eczema-prone patients, especially in compromised skin or when layered with acids/retinoids, so it is best categorized as gentle but not exceptionally inert. Safety Notes: In commercial leave-on serums, eye products, and moisturizers, bis(tripeptide-1) copper acetate (a copper-peptide complex similar in use-positioning to other GHK-Cu derivatives) is most often dosed at very low levels because it is potent, costly, and can destabilize formulas or discolor at higher loadings; market products commonly land in the ~0.0005–0.01% range. The low end (~0.00005%) reflects “label-claim” inclusion levels seen in multi-ingredient anti-aging creams where the peptide complex is present for marketing support rather than as the primary active. The high end (~0.05%) reflects high-strength consumer-available copper-peptide serums/ampoules that push copper-peptide complexes toward upper practical limits for stability/appearance in leave-on systems; rinse-off products generally use equal or lower levels due to short contact time.

Blue 1 Lake

Blue 1 Lake (the insoluble aluminum salt form of FD&C Blue No. 1) is used as a colorant, typically at very low concentrations, and is generally well-tolerated in leave-on and rinse-off products. However, synthetic dyes can trigger occasional irritation or rare hypersensitivity reactions in highly reactive or eczema-prone individuals, particularly on compromised skin or around the eyes/lips. Given the low usual exposure but non-zero risk in sensitive populations, it fits best as a mild irritant potential ingredient. Safety Notes: Blue 1 Lake (CI 42090:2) is typically used at ultra-low levels in skincare as a colorant/opacifier tweak, with commercial leave-on creams/lotions and cleansers often dosing around ~0.00001–0.01% to achieve a pale tint. Higher concentrations are observed in strongly colored OTC products (e.g., blue-toned masks, styling/edge gels marketed for skin/hairline use, and vivid tinted balms/cream products), where lakes may be pushed into the ~0.1–0.5% range to deliver saturated color and improved bleed resistance versus soluble dyes. Actual allowable use depends on jurisdiction and product category (e.g., general cosmetics vs eye-area or lip products), so brands typically stay within local color additive regulations and impurity limits.

Boerhavia Diffusa Root Extract

MVP Approved - Boerhavia Diffusa Root Extract is a plant‐derived ingredient used primarily for its soothing properties and antioxidant benefits, making it popular in formulations aimed at calming irritated skin.

Borago Officinalis Seed Extract

Borago officinalis (borage) seed extract is typically used at low concentrations as an emollient/soothing, omega-6 (GLA)-rich botanical to support barrier function, and it is generally well-tolerated in leave-on products. However, as a plant-derived extract it carries a non-zero risk of irritant reactions or allergy in highly reactive or eczema-prone individuals (botanical constituents can trigger contact dermatitis even when marketed as “calming”). Given its usually low-potency profile but real sensitization potential in susceptible patients, a gentle-but-not-inert score is appropriate. Safety Notes: In mass-market leave-on creams/lotions and facial serums, Borago Officinalis Seed Extract is often used at very low levels (around 0.001–0.1%) as a label/antioxidant-botanical claim within broader botanical blends. Mid-range “soothing/barrier” products more commonly fall around ~0.1–1%. Higher-strength consumer products (typically facial oils, oil-serums, and some anhydrous balm concentrates) can reach about 2–5% when the extract is supplied in an oil/glycol carrier and positioned as a hero botanical; rinse-off products are usually at the low end due to cost and short contact time.

Borago Officinalis Seed Oil

Borago officinalis (borage) seed oil is primarily an emollient rich in linoleic acid and gamma-linolenic acid, typically used at a few percent up to higher levels in barrier-support products. Clinical experience and patch-test data generally show low irritancy for non-fragranced, well-refined plant oils, but a small subset of highly reactive or eczematous patients can experience irritation or rare allergy (and oxidized oils can be more reactive). Given sensitive-skin safety priorities, I rate it as very gentle but not inert. Safety Notes: In mainstream leave-on creams/lotions and serums, borage seed oil is often used as a supporting emollient or omega-6/GLA source at low sub-1% levels (commonly ~0.05–0.5%) alongside other oils to manage cost/odor/oxidation, with rinse-off cleansers typically at similar or lower levels. Mid-range leave-on facial oils and barrier-repair creams frequently use ~1–10% (sometimes higher) when positioned as a key lipid. The high end in consumer OTC products reaches 100% in single-ingredient borage oil sold as a topical facial/body oil, and ~20–50% in anhydrous oil blends/balms where it is the dominant oil.

Boric Acid

Boric acid is used primarily as a mild antiseptic/buffering agent, typically at low concentrations in personal care, but it can irritate skin and especially eyes and mucous membranes, with stinging more likely on compromised barriers (eczema, post-procedure). Human experience and safety assessments note irritation potential that is dose- and exposure-dependent, so in sensitive-skin routines and leave-on contexts a patch test is prudent. Given the non-negligible irritation risk in reactive individuals and the need for caution on damaged skin, it fits a moderate irritancy score. Safety Notes: In modern OTC skincare/cosmetic products, boric acid is most often used at very low levels (about 0.01–0.5%) as a pH-adjuster/buffering or mild antimicrobial support ingredient in leave-on creams/lotions and some rinse-off cleansers, with traces down to ~0.01% appearing in broader preservative/buffer systems. At the high end of consumer-available products, boric acid is found in stronger antiseptic/astringent and anti-odor topical preparations (often marketed for skin irritation/rashes or hygiene) where 2–5% is observed; concentrations above this are uncommon in mainstream OTC cosmetics and more associated with medicinal/professional uses rather than typical cosmetic leave-on formulations.

Boron Nitride

Boron nitride is an inert, insoluble cosmetic powder used mainly for slip, blurring, and oil-absorption in makeup and some skincare, typically at low-to-moderate percentages, and it is generally well-tolerated in patch testing. Irritation potential is usually limited to mechanical/frictional effects in very reactive or barrier-impaired skin (or ocular irritation if it migrates into the eyes) rather than true chemical irritation. Given rare reports of sensitivity and the reality of compromised-skin populations, I score it as very gentle rather than completely inert. Safety Notes: In real-world consumer skincare and hybrid skincare-makeup products, boron nitride is often used at very low levels (~0.05–0.5%) in lotions/serums/primers to add slip and reduce tack, while many face powders/blur primers and silicone-heavy leave-on products commonly sit around 1–8%. The highest OTC levels are seen in anhydrous powders, stick balms, and putty/blur primers where boron nitride can function as a primary texture/soft-focus filler, reaching about 10–20% in some consumer-available products. It is overwhelmingly a leave-on cosmetic/personal care ingredient; rinse-off usage exists but typically remains at the low end because sensorial benefits are less persistent.

Boswellia Serrata Extract

Boswellia serrata extract is typically used at low concentrations as a soothing/anti-inflammatory botanical, and it is generally well tolerated in leave-on products. However, as a plant resin extract containing complex terpenoid constituents, it carries a real risk of irritant or allergic contact dermatitis in a small but meaningful subset of sensitive or eczema-prone patients, especially with repeated exposure. Given this sensitization potential and variability in extract composition, I rate it as mild rather than “gentle.” Safety Notes: In mainstream OTC moisturizers/serums and calming products, Boswellia serrata extract is commonly used at very low levels (~0.05–0.5%) as a soothing botanical within broader blends, while rinse-off cleansers typically sit at the low end due to short contact time. Higher-strength consumer-available leave-on treatments and targeted “anti-redness/anti-inflammatory” serums can reach ~1–5% when using standardized extracts (often positioned as boswellic-acid rich), with 5% representing the upper end seen before texture/odor/solubility and cost become limiting.

Brassica Campestris Seed Oil

Brassica Campestris (rapeseed) seed oil is a lipid emollient typically used at several percent up to high levels in moisturizers, where it is generally well-tolerated and supports barrier function. Clinical experience and patch testing data suggest a low irritancy profile, but like many botanical oils it can still trigger irritation or rare allergy in highly reactive or eczematous skin, especially on compromised barriers. Given the sensitive-skin benchmark and the need to avoid underestimating risk, it fits best as very gentle rather than inert. Safety Notes: In commercial skincare, Brassica Campestris (rapeseed) seed oil is frequently used at very low levels (~0.05–1%) as an emollient slip agent or lipid co-emulsifier in creams/lotions and some rinse-off cleansers where it appears mid-to-late INCI. At the high end, it is sold to consumers as pure carrier oil and as the primary oil phase in anhydrous body/face oils, balms, and oil cleansers, reaching 70–100% in OTC products. No specific global cosmetic maximum applies beyond general safety/impurity controls, so the observed market ceiling is set by neat-oil products rather than regulation.

Brassica Oleracea Acephala Leaf Extract

Brassica Oleracea Acephala (kale) leaf extract is primarily an antioxidant/soothing botanical used at low percentages, and it is generally well-tolerated in routine patch-test experience when properly purified. However, as a plant extract it contains multiple bioactive compounds that can trigger irritant or allergic contact dermatitis in a small but real subset of highly reactive or eczematous patients, especially when combined with other actives in a full routine. Given this non-zero sensitization potential typical of botanicals, it fits a 'gentle' but not 'very gentle/inert' profile. Safety Notes: In commercial skincare, kale (Brassica Oleracea Acephala) leaf extract is frequently used as a minor antioxidant/soothing botanical, often appearing in multi-extract blends at trace-to-low levels around 0.001–0.1% (especially in rinse-off cleansers and broadly positioned “greens” formulas). Leave-on serums/creams and “superfood/antioxidant” products commonly use it at ~0.1–2%, while a smaller set of consumer-available high-botanical or single-hero extract products reach ~3–5% depending on supplier strength (e.g., glycerin/butanediol extracts) and sensorial/stability constraints. No specific FDA/EU maximum applies to this botanical extract, so practical market limits are driven by odor/color, stability, and irritation potential rather than regulation.

Brassica Oleracea Capitata Leaf Extract

Brassica Oleracea Capitata (cabbage) leaf extract is primarily used as a soothing/antioxidant botanical at low concentrations, and it is generally well-tolerated in leave-on products. However, Brassica extracts can contain sulfur-containing compounds and other plant constituents that can trigger stinging or irritant reactions in highly reactive or eczematous skin, and botanicals carry a small but real risk of sensitization. Given this non-zero risk in compromised skin despite typical low use levels, I score it as gentle but not exceptionally gentle. Safety Notes: In mass-market and prestige skincare, Brassica Oleracea Capitata (cabbage) leaf extract is typically a low-level botanical “support” ingredient, often used at trace levels (~0.0001–0.05%) in emulsions and cleansers where it appears low on the INCI list. Higher levels are mainly seen in natural/“superfood” style leave-on products (serums, gels, masks) where the extract or a concentrated glycerin/propylene glycol extract is used as a featured active, with observed consumer-available use levels up to ~5%; higher would be uncommon due to odor/color, stability, and cost constraints. Rinse-off products generally sit toward the low end, while leave-on formulas account for most of the upper-range usage.

Brassica Oleracea Italica Extract

Brassica Oleracea Italica (broccoli) extract is primarily used as an antioxidant/soothing botanical at low concentrations, but Brassica-derived extracts can contain bioactive compounds (e.g., sulfur-containing constituents) that occasionally sting or trigger irritant reactions in reactive or eczematous skin. Clinical experience and patch-testing patterns with botanical extracts show a non-zero risk of irritation/sensitization despite “gentle” marketing, so I rate it as mild to reflect occasional sensitivity in compromised skin and cumulative exposure in full routines. Safety Notes: In commercial skincare, Brassica Oleracea Italica (broccoli) extract is commonly used as a minor antioxidant/soothing botanical at very low levels (often trace to ~0.1%) within multi-extract blends, where label claims are supported with minimal add levels. Higher-strength consumer products (typically leave-on serums, creams, and “superfood” masks) may use dedicated broccoli extract at ~1–5% depending on supplier form (often glycerin/butanediol-water extracts) and sensory/stability constraints; rinse-off products generally sit toward the lower end due to cost and limited deposition.