Skincare Ingredients

Ganoderma Lucidum Stem Extract

Ganoderma lucidum (reishi) stem extract is a botanical antioxidant/soothing claim ingredient typically used at low concentrations, but as a complex plant extract it contains multiple bioactive compounds that can trigger irritant or allergic contact dermatitis in a minority of reactive or eczematous patients. Clinical patch-test data on this specific stem extract is limited and product-to-product variability (extraction solvents, contaminants, residual proteins) increases uncertainty, so I rate it as mild irritation potential rather than categorically “gentle,” especially for compromised skin. Safety Notes: In mass-market leave-on skincare, Ganoderma Lucidum (reishi) stem extract is often used at very low levels (around 0.0005–0.05%) as part of multi-botanical “complexes,” where it functions primarily as a marketing/soothing antioxidant support ingredient and is typically listed mid-to-late INCI. Higher-strength consumer serums/ampoules and “single-hero” botanical formulas can reach ~1–5% when the supplier material is a standardized extract designed for direct addition at percent-level (with the upper end limited by solubility, color/odor, and stability rather than regulation). Rinse-off products generally sit toward the lower half of the range due to short contact time, while leave-on products more commonly occupy the upper half.

Garcinia Indica Seed Butter

Garcinia Indica (kokum) seed butter is a largely inert emollient/occlusive used at moderate to high levels to soften skin and support barrier function, and it is generally well tolerated compared with fragranced plant oils. However, as a botanically derived lipid, it can still trigger irritation or contact allergy in a small subset of highly reactive or eczema-prone patients (often related to minor constituents or oxidation/impurities), so it should not be scored as near-inert. In routine leave-on products its overall irritancy risk is low but not zero, warranting a gentle score rather than exceptionally gentle for compromised skin. Safety Notes: In commercial emulsions (lotions/creams), Garcinia Indica (kokum) seed butter is commonly used as a minor structuring emollient at low levels around 0.1–2% (often alongside other butters/oils) to improve slip and reduce greasiness in leave-on products. Mid-to-high levels (5–30%) are found in body butters, balms, and lip products where it functions as a primary occlusive/structurant. The market high end includes anhydrous consumer butters sold as single-ingredient “kokum butter,” which are effectively 100% and intended for leave-on use; rinse-off products rarely exceed low single digits due to sensory and deposition limits.

Garcinia Mangostana Peel Extract

Garcinia mangostana (mangosteen) peel extract is used mainly as an antioxidant/anti-inflammatory botanical, typically at low concentrations, but it contains polyphenols/xanthones that can act as contact irritants or sensitizers in reactive or eczema-prone skin. Human irritation data are limited compared with standard emollients, so I score it as mild risk: generally tolerated, yet capable of stinging, redness, or delayed dermatitis in compromised barriers or when layered with other actives. Safety Notes: In mass-market leave-on skincare (serums, lotions, toners) mangosteen peel extract is commonly used as a supporting antioxidant/soothing botanical at very low levels (often ~0.001–0.1%), especially when supplied as a dilute liquid in glycerin/propylene glycol. Higher-strength consumer products marketed around ‘mangosteen’ (concentrated serums, ampoules, masks) can reach ~1–5% active extract, with ~5% representing the upper end typically seen OTC due to color/odor, polyphenol-driven stability/compatibility constraints, and cost. Rinse-off products generally sit toward the lower end of the range because brief contact time reduces the need for higher loading.

Gardenia Florida Fruit Extract

Gardenia florida fruit extract is primarily used as a botanical antioxidant/skin-conditioning ingredient, typically at low concentrations, but it is a complex plant extract containing multiple small molecules that can provoke irritation in reactive or eczema-prone skin. While not a classic high-risk allergen like fragrance mixes, botanical extracts show nontrivial rates of stinging/irritant reactions in sensitive-skin and patch-test populations, especially when layered with other actives or on a compromised barrier. Given the unpredictability of plant-extract variability and the need to err on patient safety, it warrants a mild irritancy classification. Safety Notes: In mass-market leave-on skincare, Gardenia florida fruit extract is typically used as a minor botanical/antioxidant or fragrance-supporting extract at trace-to-low levels (often ~0.001–0.1%), especially when supplied as a glycerin/propylene glycol extract and positioned low on the INCI list. Higher-strength consumer “botanical active” serums, masks, and some K-beauty brightening/soothing products can push total use levels into the ~1–5% range (depending on extract potency/solids), with rinse-off products generally tolerating similar or slightly higher levels due to shorter skin contact. There are no specific FDA/EU cosmetic concentration caps for this extract itself; practical maxima are usually set by odor/color impact, stability, and irritation potential of the specific supplier extract.

Gaultheria Procumbens Leaf Oil

Gaultheria procumbens (wintergreen) leaf oil is an essential oil composed largely of methyl salicylate, used primarily for fragrance and counterirritant/analgesic effects, and it can be irritating even at low leave-on concentrations. Essential oils and salicylate-rich materials have a well-documented risk of irritant contact dermatitis and can exacerbate eczema through barrier disruption, with additional sensitization risk from naturally occurring fragrance constituents. Given the high likelihood of stinging, redness, and flare potential in compromised skin and the lack of necessity for barrier-repair routines, it warrants a very high irritancy score. Safety Notes: Gaultheria Procumbens (wintergreen) leaf oil is a high-odor, salicylate-rich essential oil typically used at trace levels (~0.001–0.05%) in leave-on facial skincare and "natural" fragranced products for scent and marketing claims. In rinse-off body washes/scrubs and muscle/balm-style OTC products it is commonly higher (about 0.1–1.0%) and can reach ~2% in strong consumer-available liniments/balms where it functions primarily as a counterirritant/aroma active; higher levels are uncommon due to irritation/sensitization risk and IFRA-style restriction practices for methyl salicylate-containing materials.

Gelatin

Gelatin is a denatured collagen-derived film-former/binder used in masks and topical formulations typically at low-to-moderate percentages, and it is generally well tolerated with minimal inherent irritancy. Clinical experience and patch-test data suggest irritation is uncommon, but animal-protein derivatives can occasionally trigger reactions in highly atopic or protein-sensitized individuals, so it cannot be considered fully inert. Given this small but real risk in severely sensitive populations, it fits best as very gentle rather than inert. Safety Notes: In commercial skincare, gelatin is most often used as a film-forming/texture aid in leave-on masks, peel-off masks, and some creams/lotions, with low-end use around 0.05–0.5% for light skin-feel or claim support (often alongside other polymers). The highest consumer-available levels are seen in DIY-style or ready-to-mix peel-off mask powders and strong-setting gel masks where gelatin functions as the primary gelling/film-forming agent, commonly 3–10% depending on bloom strength and desired set. Rinse-off mask formats tolerate the upper end more readily than leave-on products, which typically stay in the low single-digit percent range due to tack/feel and stability constraints.

Gellan Gum

Gellan gum is an anionic polysaccharide used primarily as a gelling/thickening agent, typically at low concentrations (about 0.05–1%) where it is generally biologically inert on skin. Clinical and real-world tolerability data for polysaccharide thickeners show very low rates of irritation or sensitization, with reactions being uncommon and usually tied to compromised barriers or formula context rather than the gum itself. For severe eczema-prone or post-procedure skin I still assign a minimal, non-zero risk because any film-former/texture agent can rarely cause stinging or friction-related irritation in highly reactive patients. Safety Notes: In commercial skincare, gellan gum is often used as a low-level rheology modifier/suspending aid in watery serums, mists, toners, and micellar-type products at ~0.01–0.10%, where it provides light body and particle suspension without noticeable gel texture. Higher levels are seen in consumer gel-type formulas (e.g., gel moisturizers, gel masks, gel cleansers, peel-off/setting gels, and some hydrogel-style textures) where it functions as a primary gelling agent, commonly ~0.2–0.8% and up to about 1.0% in high-structure OTC gels; usage is generally similar for leave-on vs rinse-off with final viscosity/feel dictating placement within the range.

Genistein

Genistein is an isoflavone antioxidant/phytoestrogen typically used at low concentrations (often ~0.1–1%) in anti-aging/brightening formulas and is not inherently caustic like acids or retinoids. However, human tolerance data are limited and plant-derived phenolics can provoke stinging or dermatitis in reactive/eczema-prone users, especially in leave-on products and multi-active routines. Given the uncertainty and the need to err on patient safety for highly sensitive skin, I rate it as mild with occasional sensitivity possible. Safety Notes: In mass-market and prestige anti-aging leave-on products, genistein (often listed as genistein/soy isoflavones or delivered via soybean extracts) is frequently present at very low active-equivalent levels (~0.001–0.05%) as a supporting antioxidant/phytoestrogenic component. Clinically oriented cosmeceuticals and niche “isoflavone/phytoestrogen” serums and creams marketed for menopause-related skin changes and firming commonly use higher standardized genistein levels around 0.5–2%. A small number of high-strength, consumer-available specialty formulas (typically anhydrous/encapsulated leave-on serums) reach about 5% genistein; rinse-off products are uncommon and generally sit at the low end due to short contact time.

Gentiana Lutea Root Extract

Gentiana lutea root extract is a botanical bitter extract (often used for antioxidant/soothing or “revitalizing” claims) typically present at low percentages, but plant extracts carry variable composition and can trigger stinging or irritant dermatitis in reactive or eczematous skin. While not a high-frequency allergen like fragrance mixtures, case reports and patch-test experience with botanical extracts support a non-zero risk of irritation/sensitization, especially on compromised barriers and in multi-ingredient routines. For patient safety in very sensitive populations, I rate it as mild rather than gentle. Safety Notes: In commercial skincare, Gentiana lutea (gentian) root extract is commonly used as a minor botanical adjunct in toners, lotions, and cleansers at trace-to-low levels (~0.0005–0.05%), reflecting typical supplier recommended-use rates and the fact it’s often part of multi-extract blends. Higher concentrations are seen in consumer-available “high-botanical/active extract” leave-on serums and creams where the extract (or a glycerin/butanediol extract) is positioned as a key soothing/brightening component, with observed use levels up to ~5% without being prescription/professional-only. Rinse-off formats generally cluster toward the low end due to short contact time and cost, while leave-on products account for most of the upper range.

Geraniol

Geraniol is a fragrance allergen naturally present in many essential oils and is used at low concentrations for scent, but even trace levels can provoke stinging or dermatitis in sensitized or barrier-impaired skin. Patch testing and clinical experience consistently identify geraniol as a relevant contact allergen, with higher risk in eczema-prone individuals and in leave-on products where cumulative exposure occurs. Given its sensitization potential and the high stakes for reactive skin populations, it warrants a high irritancy score. Safety Notes: In mass-market skincare, geraniol is most often present as a trace constituent of fragrance/essential-oil blends, with finished-product levels commonly in the ~0.0001–0.05% range (especially in leave-on products where allergen labeling thresholds apply). Higher consumer-available levels occur in heavily fragranced natural/essential-oil-focused balms, body products, and perfumed creams where fragrance loads are higher and the geraniol fraction can push the finished-product concentration to ~0.2–0.8%. Levels above this are atypical for mainstream OTC skincare due to sensitization risk and IFRA-driven formulation limits, especially for leave-on facial products.

Gigartina Stellata Extract

Gigartina stellata extract is a red seaweed extract primarily used as a film-forming, soothing/hydrating agent in low concentrations (typically well under a few percent) and is generally well tolerated. However, like other marine botanicals, it can contain complex polysaccharides/trace components that occasionally trigger irritation or allergy in highly reactive or eczema-prone patients, so it is not truly inert. In routine leave-on formulas it carries a low but non-zero risk, consistent with a gentle (0.3) score. Safety Notes: Gigartina stellata extract (a red seaweed-derived skin-conditioning/film-forming extract) is most often used at very low levels in mass-market leave-on lotions/serums and rinse-off cleansers as part of a broader marine/alginate extract blend, commonly around 0.001–0.1%. In more “marine concentrate” or hydrating mask/gel products marketed around seaweed actives, I’ve observed suppliers’ recommended use levels and finished-product positioning supporting higher loadings in the ~1–5% range (still within typical cosmetic stability/sensory constraints for aqueous gels/emulsions). No specific EU/FDA maximum applies for this botanical extract in cosmetics; practical limits are driven by odor/color, viscosity/gelation, and preservative demand, with leave-on products generally formulated lower than rinse-off when sensitization risk is a concern.

Ginkgo Biloba Leaf Extract

Ginkgo biloba leaf extract is primarily used as an antioxidant/soothing botanical at low concentrations, but botanical extracts are a common source of variability and can trigger irritation in reactive or barrier-impaired skin. Patch testing and case reports document occasional allergic contact dermatitis to ginkgo (especially in eczema-prone individuals), so despite being marketed as “gentle,” it carries a real sensitization risk. In routine multi-ingredient regimens, this makes it a mild but non-trivial irritant for sensitive populations. Safety Notes: In mass-market creams, toners, and cleansers, Ginkgo Biloba Leaf Extract is often used at very low levels (around 0.0005–0.05%) as part of multi-extract blends or at typical supplier-recommended add levels for botanical extracts, especially in rinse-off formats where cost and deposition are limiting. Mid-range leave-on serums and moisturizers commonly sit around ~0.1–1% depending on whether the listing refers to the raw extract or a standardized/dry extract. The upper end (~2–5%) is observed in consumer-available “high botanical” serums/ampoules and some gel creams where ginkgo is a featured claim ingredient; higher levels are uncommon due to color/odor, solubility, and stability constraints and are typically found in leave-on products rather than rinse-off.

Glabridin

Glabridin is a licorice-root–derived flavonoid used mainly for brightening and anti-inflammatory effects, typically at low concentrations (about 0.1–1%) in leave-on products. While generally well-tolerated, botanical actives can trigger irritant or allergic contact dermatitis in a subset of sensitive or eczematous patients, and real-world formulations often pair it with penetration enhancers that can amplify reactivity. Given the potential for sensitization in compromised skin despite low typical dosing, a mild irritancy score is the safer clinical assessment. Safety Notes: In consumer leave-on brightening/anti-spot products, glabridin (typically as licorice extract standardized to glabridin) is commonly present at low active-equivalent levels around 0.01–0.10%, reflecting cost, solubility, and stability constraints; many mass-market serums/lotions fall in this band. Higher-strength OTC offerings (specialty hyperpigmentation serums/ampoules using purified glabridin or high-standardized extracts, often solubilized) reach ~0.5% and up to about 1.0% in real-world products marketed to the public. Rinse-off products tend to sit near the low end due to short contact time, while the upper end is primarily observed in leave-on treatments.

Gleditsia Triacanthos Seed Extract

Gleditsia Triacanthos (honey locust) seed extract is a botanical used mainly as a film-forming/conditioning and texture-enhancing ingredient, typically at low concentrations (often <1–2%) in leave-on products. While it is not a well-characterized high-risk active, botanical extracts contain complex proteins/polyphenols that can trigger irritation or allergic contact dermatitis in reactive or eczema-prone patients, and the lack of robust standardized patch-test data warrants a cautious rating. In routine skincare layering, it is unlikely to be a primary irritant for most users, but occasional sensitivity is plausible in highly reactive individuals. Safety Notes: In commercial INCI-labeled skincare, Gleditsia Triacanthos Seed Extract is typically used as a botanical/functional extract (often supplied in a solvent carrier), so it appears at very low levels (~0.001–0.05%) in mass-market leave-on products where it is part of a broader plant-extract blend. More prominent positioning in “tightening/firming” serums, masks, and specialty leave-on treatments can push use levels into the ~0.5–2% range, with the highest consumer-available formulations observed around ~5% when brands use a concentrated extract solution as a key active. No specific global maximum is set for this INCI, so the practical upper bound is driven by supplier recommended use levels, sensorial/tackiness limits, and stability rather than regulation.

Gluconolactone

Gluconolactone is a polyhydroxy acid (PHA) chemical exfoliant typically used around 2–15% at acidic-to-near-neutral pH, and is generally less irritating than glycolic or lactic acid due to larger molecular size and slower penetration. However, as an active exfoliant it can still cause stinging, dryness, or eczema flare in reactive or barrier-impaired patients, especially when combined with other actives or frequent use. For patient safety in sensitive populations, it warrants a mild irritancy score rather than being categorized as inherently gentle or inert. Safety Notes: In commercial skincare, gluconolactone (a PHA) is used at very low levels (~0.1–1%) as a mild chelating/antioxidant-supporting humectant in sensitive-skin moisturizers, toners, and barrier serums, where it is not positioned as the primary exfoliant. Most leave-on PHA exfoliating toners/serums and combination AHA/BHA/PHA products sit around ~2–10% (often pH-buffered for tolerability), aligning with published PHA exfoliation/anti-aging studies and common industry practice. The highest consumer-available strengths observed are ~15–20% in at-home “peel”/resurfacing treatments (typically leave-on for short contact time or rinse-off masks), which represent the upper end of OTC market offerings while remaining below professional-only peel conventions.

Glucosamine

Glucosamine is typically used in leave-on skincare at low percentages (often ~1–5%) as a humectant/skin-conditioning and tone-support ingredient, and it is generally well tolerated in patch testing and clinical use. However, in highly reactive or eczematous skin it can still sting or irritate—especially in compromised barriers or when combined with other actives—so I rate it as gentle but not “very gentle/inert” for patient safety. Safety Notes: In mass-market and prestige leave-on serums/creams, glucosamine is commonly present at low supportive levels around 0.1–1% (often paired with niacinamide for tone/brightening claims), and it also appears at similar or slightly lower levels in some rinse-off cleansers. High-strength OTC brightening/spot-correcting leave-on treatments have been marketed in the ~2–5% range, with ~5% representing the upper end typically seen due to solubility, pH/salt form (HCl vs sulfate), and sensory/stability constraints rather than regulatory limits.

Glucosamine Hcl

Glucosamine HCl is primarily used as a skin-conditioning/brightening support ingredient (often ~1–5%) and is generally well tolerated, with low rates of irritation in cosmetic use compared with exfoliating acids or retinoids. However, as a hydrochloride salt it can contribute to stinging in compromised barriers (eczema, post-procedure) and there are occasional reports of sensitivity, so I do not consider it fully “exceptionally gentle.” For patient safety in highly reactive skin, I score it as very gentle but not inert. Safety Notes: In consumer skincare, glucosamine HCl is most often used as a leave-on brightening/skin-tone support active, with low-end inclusions around 0.1–0.5% in multi-active serums and moisturizers where it plays a supporting role. Common efficacious commercial levels are ~1–4%, while a smaller number of high-strength OTC specialty products (typically water-based serums/lotions) reach the upper end around 8–10% before sensoriality, stickiness, and pH/solubility constraints tend to limit further increases. It is less commonly used in rinse-off products, where levels are usually toward the lower end due to short contact time.

Glucose

MVP Approved - Glucose is used in skincare primarily as a humectant to boost skin hydration, and it is generally well tolerated with a low potential for irritation.

Glucose Oxidase

Glucose oxidase is an enzyme used in low concentrations in cosmetics (often as part of preservative/antimicrobial or oxygenating systems), and as a protein it can be irritating for some compromised or highly reactive skin despite generally low direct irritancy in routine use. Enzymatic activity can also generate hydrogen peroxide locally (depending on formulation and available glucose/oxygen), increasing stinging risk on eczematous or barrier-impaired skin. Given these sensitization/irritation considerations in sensitive populations, I rate it as mild rather than “gentle.” Safety Notes: In consumer skincare, glucose oxidase is most often used as an enzymatic oxygen-generating/antimicrobial support ingredient in very low amounts, typically in leave-on serums/creams and sheet-mask essences where it appears around trace-to-low levels (~0.0001–0.05%) due to potency and stability limits (activity depends on enzyme units, water activity, pH, and available glucose). The upper end of the observed OTC market occurs in specialty enzyme-based products (e.g., “oxygenating” masks/cleansers or activated systems where glucose oxidase is paired with glucose), where the listed enzyme material can reach about 0.5–1.0% in the formula (often reflecting a diluted, standardized enzyme preparation rather than 100% active protein). There is no specific EU/FDA cosmetic maximum for glucose oxidase, but practical formulation constraints (irritation potential from generated hydrogen peroxide, preservation compatibility, and enzyme denaturation) generally prevent higher levels in consumer leave-on products.

Glucosyl Ceramide

Glucosyl ceramide is a barrier-replenishing lipid used at low concentrations in moisturizers/serums and is generally well-tolerated, including in eczema-prone and compromised skin. Human patch-test/clinical use data for ceramide-type lipids show low inherent irritancy, with reactions more often attributable to the overall formula (preservatives, solvents, fragrance) rather than the ceramide itself. Because rare intolerance can occur in highly reactive patients, it is not scored as inert, but remains very gentle at typical use levels. Safety Notes: In consumer moisturizers/serums (leave-on), glucosyl ceramide is often used at very low levels (~0.001–0.05%) as part of multi-lipid/ceramide complexes or "pseudo-ceramide" blends where it is a minor component. Higher-strength OTC barrier-repair creams and targeted ceramide boosters can reach ~0.5–2.0% when the supplier material is high-purity (or when the formula is built around a concentrated glucosylceramide active), with practical upper limits driven by cost, dispersibility, and texture/stability rather than specific regulatory caps. Rinse-off products (cleansers/body wash) typically sit at the low end because deposition is limited.

Glucosyl Hesperidin

Glucosyl hesperidin is a water-soluble flavonoid derivative used mainly for antioxidant/vasoprotective and anti-redness claims, typically at low leave-on concentrations (about 0.1–1%). Available safety/patch-test experience for this class suggests low irritancy and low sensitization potential, with reactions being uncommon but possible in highly reactive eczema-prone skin. Given the need to be cautious with severely sensitive populations while acknowledging its generally good tolerability, it fits best as a very gentle ingredient rather than inert. Safety Notes: In commercial skincare, glucosyl hesperidin is commonly used as a microcirculation/anti-redness support active in leave-on eye creams, facial serums, and moisturizers at very low levels (~0.001–0.05%), reflecting its use as a supporting botanical-derived active in multi-ingredient formulas. Mid-to-higher strength consumer products (especially targeted anti-redness/under-eye treatments) more often sit around ~0.1–0.5%, while a small number of high-strength OTC specialty products and concentrate-style ampoules reach about 1–2% where solubility, cost, and sensorial/stability constraints typically become limiting; rinse-off products tend to use the low end due to short contact time.

Glucosylrutin

Glucosylrutin is a water-soluble flavonoid (rutin derivative) used mainly as an antioxidant/anti-inflammatory and anti-redness support ingredient, typically at low concentrations (~0.1–1%). Available human tolerance/patch-test experience with rutin derivatives suggests a low irritation profile, with adverse reactions being uncommon and usually limited to rare individual hypersensitivity rather than predictable irritancy. Given use in sensitive-skin formulas but acknowledging the non-zero potential for idiosyncratic reactions in compromised barriers, a very gentle score is most consistent with patient-safety expectations. Safety Notes: In commercial skincare, glucosylrutin (a more water-soluble rutin derivative used for antioxidant/anti-redness and capillary-support claims) is commonly present at low “supporting active” levels around 0.01–0.1% in leave-on serums/creams and around ~0.01–0.05% in rinse-off cleansers where contact time is short. Higher-strength consumer-available leave-on products (especially anti-redness, brightening, or antioxidant concentrates) are typically formulated in the ~0.5–1% range, with the upper end observed around ~2% in specialty high-active serums where solubility and color/odor constraints still allow use; no specific EU/FDA maximum is set for this ingredient, so practical formulation limits drive the top end.

Glutamic Acid

MVP Approved - Glutamic acid is an amino acid used primarily as a humectant and skin-conditioning agent in skincare formulations, known for its mild nature and low irritation potential.

Glutamine

Glutamine is an amino acid used mainly as a skin-conditioning/humectant-support ingredient, typically at low concentrations, and it is generally well tolerated because it is not inherently acidic, solvent-like, or strongly reactive. Clinical irritation signals for glutamine itself are uncommon in patch-testing literature compared with fragrances, preservatives, and actives, but compromised eczema skin can still sting to otherwise mild amino-acid solutions depending on formula osmolality and pH. To avoid underestimating risk in highly sensitive populations while reflecting its overall gentle profile, it is scored as very gentle. Safety Notes: In commercial skincare, glutamine is most often used as a skin-conditioning/amino-acid support ingredient in multi-amino-acid blends and barrier-support serums/creams, where it can appear at low “label presence” levels around ~0.01–0.1% in leave-on products. Higher-strength consumer-available formulas (typically leave-on serums or creams marketed for barrier repair, post-procedure comfort, or microbiome/skin recovery) have been observed using glutamine around ~0.5–2% as a dedicated active within amino-acid/NMF complexes. Above ~2% is uncommon in mass-market OTC due to diminishing formulation benefit, solubility/osmolality considerations, and the tendency for brands to shift to broader amino-acid systems rather than pushing single-amino-acid load.

Glutathione

Topical glutathione (a tripeptide antioxidant/brightening agent) is typically used at low percentages and is generally well-tolerated, with patch-test/consumer data suggesting low rates of irritation compared with stronger actives. However, in compromised skin (e.g., eczema or post-procedure), thiol-containing compounds can still sting or provoke irritant reactions depending on vehicle, pH, and co-ingredients, so it cannot be considered exceptionally gentle/inert. I score it as gentle to reflect low inherent irritancy but non-zero risk in highly reactive patients and in multi-active routines. Safety Notes: In consumer skincare, glutathione (reduced/oxidized forms or liposomal derivatives) is often used at low supportive levels around 0.01–0.1% in brightening serums/creams and in rinse-off cleansers where deposition is limited. Most leave-on brightening products cluster around ~0.1–1% due to cost, odor, and oxidation/stability constraints, while a smaller set of high-strength OTC “glutathione” serums/ampoules marketed for tone improvement reach ~2–5% using anhydrous, encapsulated, or airless packaging to mitigate instability. Higher levels than ~5% are uncommon in true topical formulas because solubility and rapid oxidation significantly limit practical performance, and many products marketed as high-dose may refer to blends/complexes rather than pure glutathione.

Glycereth-26

Glycereth-26 is a PEG-modified humectant/emollient used primarily to improve slip and hydration, commonly included at a few percent up to ~10% in leave-on products. Human data and broad clinical experience place it as generally well-tolerated, with irritation uncommon but possible in highly reactive or barrier-impaired eczema skin (often related to cumulative formula factors rather than the ingredient itself). Given the sensitive-skin mandate and the non-zero but low likelihood of stinging in compromised barriers, it fits best as very gentle rather than inert. Safety Notes: Glycereth-26 is a water-soluble humectant/solubilizer commonly used at low levels (~0.1–2%) in leave-on lotions, serums, toners, and cleansers to boost slip, moisturization, and aid solubilization of fragrance/actives. In consumer-available high-humectancy gel creams, makeup primers, hydrating masks, and some “concentrated” moisturizers, it can be a major polyol component used around 10–25% to build cushion and reduce tack versus glycerin alone. It is not subject to an EU/FDA specific concentration limit for cosmetics, so the upper end is mainly governed by sensorial/stickiness, preservative system water activity, and viscosity/clarity constraints (leave-on typically higher than rinse-off).

Glycereth-7 Triacetate

Glycereth-7 triacetate is an ethoxylated glycerin ester used mainly as an emollient/solvent and viscosity modifier, typically at low single-digit percentages in leave-on and rinse-off products. It is not an acid, fragrance, or preservative, and available patch-test/clinical experience with similar glycereth esters suggests a low rate of irritation with rare reactions in highly compromised skin barriers. Given the ethoxylated nature and ester content (which can occasionally sting on fissured eczema skin), I rate it very gentle rather than inert to avoid underestimating risk in severely sensitive patients. Safety Notes: Glycereth-7 Triacetate is most often used as a solubilizer/emollient/plasticizing carrier for fragrance, lipophilic actives, or to improve sensory slip, so it commonly appears at very low levels (~0.05–0.5%) in leave-on lotions/serums and in rinse-off cleansers where it mainly supports aesthetics. In consumer products designed for pronounced slip or oil-phase modification (e.g., facial oils, primers, anhydrous balms, high-emolliency creams), it can be pushed into the low single-digits and up to about 10% in OTC formulas before cost, feel (oily/tacky), and phase/stability constraints typically become limiting; higher levels are uncommon outside specialty anhydrous systems.

Glycereth-7 Trimethyl Ether

Glycereth-7 Trimethyl Ether is an ethoxylated glycerin derivative used primarily as a humectant/solvent and slip agent, typically at low-to-moderate concentrations in leave-on and rinse-off products. Available safety and patch-test experience with similar glycereth compounds suggests a low irritation profile, with reactions more likely tied to compromised barriers or formula context rather than the ingredient itself. For highly reactive or eczema-prone skin, I still score it as very gentle (not inert) because ethoxylated surfactant-like materials can occasionally sting on impaired skin. Safety Notes: Glycereth-7 Trimethyl Ether is used as a water-soluble emollient/humectant and solubilizing slip agent, often appearing at low levels (~0.05–0.5%) in cleansers/toners and as a supporting solvent-feel modifier in leave-on serums/lotions. In leave-on moisturizers, primers, and makeup/skin-prep hybrids it is commonly used around 1–5%, while high-slip, solvent-heavy consumer “essence/ampoule” and specialized texture-enhancing leave-on products can reach ~10–15% where it functions as a primary sensorial and humectant component; above this, tack/feel and phase behavior typically become limiting in conventional emulsions.

Glycerin

MVP Approved - Glycerin is a well-known humectant that helps draw moisture into the skin, offering broad use in skincare with very low risk of irritation.

Glyceryl Ascorbate

Glyceryl ascorbate is a vitamin C derivative (ester) typically used around ~0.5–3% to provide antioxidant/brightening benefits with improved tolerability compared with low-pH L-ascorbic acid. Available irritation and patch-test experience suggests low direct irritancy at cosmetic use levels, but ascorbate derivatives can still sting on compromised barriers and may contribute to cumulative irritation when layered with other actives (acids/retinoids). For high-sensitivity and eczema-prone patients, I rate it as gentle rather than very gentle to reflect occasional reactivity in damaged skin. Safety Notes: In commercial OTC skincare, glyceryl ascorbate is most often used as a vitamin C derivative/antioxidant booster at low levels (~0.05–0.3%) in emulsions and serums where it functions primarily as a supportive brightening/anti-oxidative ingredient alongside other ascorbates. Higher-strength consumer leave-on serums and ampoules commonly reach ~1–3%, with the upper end around ~5% seen in specialty “high-vitamin C derivative” products where stability and sensory constraints (and total antioxidant load) tend to limit further increases. It is far less common in rinse-off formats, where levels are typically at the low end due to short contact time and cost/benefit.