Skincare Ingredients

Litsea Cubeba Fruit Extract

Litsea cubeba fruit extract is primarily used for fragrance/antimicrobial effects and is typically rich in citral and other terpenes that are well-documented irritants and potential sensitizers in patch testing. Even at low leave-on concentrations, these constituents can trigger stinging, erythema, or eczema flares in reactive skin, with higher risk when combined with other fragranced products. Given its fragrance-like allergen profile and the disproportionate risk in eczema patients, it warrants a significant irritancy score. Safety Notes: In commercial products, Litsea cubeba fruit extract is most often used as a minor botanical/antioxidant component or part of a standardized blend, with effective use levels commonly landing in the 0.01–0.5% range; at the very low end (~0.0001–0.005%) it appears as a trace component carried within multi-extract complexes or preservative/fragrance-associated blends. Higher-strength consumer-available formulations (especially rinse-off cleansers, scalp products, or “botanical concentrate” leave-on serums) can reach ~1–2% total extract, with levels above this being uncommon due to odor, sensitization potential from associated volatile constituents, and general stability/compatibility constraints in leave-on products.

Lonicera Caprifolium Flower Extract

Lonicera caprifolium (honeysuckle) flower extract is typically used at low concentrations as a botanical antioxidant/soothing agent, but it contains naturally occurring fragrant constituents that can act as irritants or allergens in reactive and eczematous skin. Patch testing and clinical experience with fragranced botanicals show a meaningful minority of sensitive patients can flare, especially with compromised barriers or when layered with other actives. Given the sensitization potential inherent to aromatic plant extracts and the need to err on safety for eczema-prone users, a moderate irritancy score is appropriate. Safety Notes: In commercial skincare, Lonicera caprifolium (honeysuckle) flower extract is most often used as a minor botanical/antioxidant component or as part of a preservative-support blend, where it can appear at trace to very low levels (~0.001–0.05%) in both leave-on and rinse-off products. Dedicated “botanical-heavy/clean beauty” toners, essences, and serums sometimes include honeysuckle extract as a featured extract or within concentrated extract complexes, with typical supplier use levels and observed INCI positioning supporting ~0.5–2.0% for consumer products. Above ~2% is uncommon in OTC due to cost, odor/color impact, and increasing irritation/sensitization risk typical of higher botanical extract loads.

Lonicera Japonica Flower Extract

Lonicera Japonica (honeysuckle) flower extract is a botanical antioxidant/skin-conditioning extract typically used at low concentrations, but it has documented potential for contact dermatitis and can act as a fragrance-like sensitizer depending on extraction method and co-occurring aromatic constituents. In highly reactive or eczematous skin, botanicals with complex mixtures increase the risk of delayed sensitization and cumulative irritation when layered with other actives, so I treat it as a moderate-risk ingredient where patch testing is prudent. Safety Notes: In commercial skincare, Lonicera Japonica Flower Extract is often used as a minor botanical/antioxidant component or as part of preservative-support systems, with many leave-on and rinse-off products listing it at trace-to-low levels around 0.001–0.1% (especially when supplied in diluted carrier bases). Higher-end “botanical concentrate” serums, masks, and some natural deodorant/toner style products can push total use levels into the ~1–5% range when the extract is used as a primary marketing active, though this is constrained by odor/color, botanical variability, and irritation/sensitization risk at higher loads. No specific EU/FDA maximum is set for this INCI, so the observed range is driven mainly by supplier recommended use levels, stability, and sensory tolerability rather than explicit regulatory caps.

Lupinus Albus Seed Extract

Lupinus Albus (white lupin) seed extract is used mainly for conditioning/soothing and anti-aging claims at low concentrations, and it is not inherently caustic like acids or retinoids. However, as a legume-derived botanical containing proteins, it carries a non-trivial risk of irritation or sensitization in reactive skin and in individuals with atopic disease or legume allergy, with patch-test reactions reported for some plant extracts in this category. Given the possibility of delayed hypersensitivity despite “gentle” marketing, I rate it as mild irritancy to prioritize patient safety. Safety Notes: In commercial skincare, Lupinus Albus (white lupin) seed extract is most often supplied as a diluted glycerin/propylene glycol/water botanical extract or as a peptide-rich active, and it commonly appears at very low levels (around 0.01–0.1%) in mass-market moisturizers/serums where it supports marketing claims without materially impacting formula aesthetics or cost. More performance-positioned leave-on products (firming/anti-aging serums and eye creams) frequently use it around 0.5–2%, with the upper end (~3%) seen in high-strength consumer formulations that use the extract as a hero active; rinse-off products typically sit at the low end due to short contact time. No specific EU/FDA maximum applies for this botanical extract, so practical limits are driven by supplier recommended use levels, stability, odor/color, and potential sensitization risk at higher loads.

Lupinus Albus Seed Oil

Lupinus Albus (white lupin) seed oil is primarily an emollient used at low-to-moderate levels in moisturizers and serums, and as a non-volatile lipid it is typically well-tolerated with low inherent irritancy. However, seed-derived botanical oils can trigger irritation or allergic contact dermatitis in a minority of highly reactive or atopic patients due to residual proteins/unsaponifiables and oxidation byproducts, especially in compromised skin barriers. Given this low but non-zero risk in sensitive populations, it fits best as a generally gentle ingredient rather than “very gentle.” Safety Notes: In commercial skincare, Lupinus Albus (white lupin) seed oil is often used at very low levels (~0.05–0.5%) as a minor emollient/marketing oil within blends and complex leave-on formulas (creams, serums, lotions), where cost, odor, and oxidative stability encourage low dosing. At the high end, it is sold to consumers as a single-ingredient or near-neat facial/body oil and as the primary carrier oil in anhydrous balms/oil serums, reaching 90–100% (with 100% representing pure bottled seed oil). No specific EU/FDA cosmetic concentration limit is established for this fixed oil; practical limits are set by sensorial profile and oxidation control (antioxidants/packaging) rather than regulation.

Lycium Barbarum Fruit Extract

Lycium barbarum (goji) fruit extract is typically used at low concentrations as an antioxidant/soothing botanical, but like many plant extracts it contains a complex mix of bioactive compounds that can provoke irritation or allergy in reactive or eczema-prone skin. While widespread severe reactions are not common, there are documented cases of hypersensitivity to Lycium species and cross-reactivity in sensitized individuals, and leave-on products can amplify cumulative irritation when layered with other actives. Given the variability in extract composition and the sensitive-skin population risk, I score it as mild with occasional sensitivity possible. Safety Notes: In mass-market leave-on products (creams, lotions, toners, sheet-mask essences), Lycium barbarum (goji) fruit extract is often used as a label/antioxidant support ingredient at very low levels (~0.0005–0.05%), especially when supplied as a diluted extract in glycerin/propylene glycol. Higher-strength consumer serums and “goji” booster products commonly use ~0.5–2% extract, with some marketed as concentrated botanical actives reaching ~5% in leave-on formats; rinse-off products typically sit toward the low end due to brief contact time. No specific EU/FDA maximum applies to this botanical extract, so practical limits are mainly set by stability, color/odor impact, and irritation potential at higher loadings.

Lycopene

Lycopene is a carotenoid antioxidant typically used at low concentrations in leave-on products, where it is generally well tolerated and not inherently pH-dependent or exfoliating. Clinical and patch-test experience suggests low irritation potential, but because it is often delivered in oily/solubilized systems that can bother highly reactive or eczema-prone skin, it is not considered completely inert. Scoring it as very gentle reflects a strong safety profile while still accounting for rare sensitivity in compromised barriers. Safety Notes: In consumer skincare, lycopene is most often used as an antioxidant/color-active in very low amounts, with many creams/lotions/cleansers listing tomato/lycopene sources that typically translate to ~0.0001–0.01% lycopene in the finished product. Leave-on serums and antioxidant concentrates (often using solubilized lycopene in oils or encapsulated/dispersed forms) commonly fall around ~0.01–0.1%, while a smaller number of high-strength OTC facial oils/serums reach ~0.2–0.5% before stability (oxidation/isomerization), staining/color, and odor constraints become limiting; rinse-off products tend to sit at the low end due to short contact time.

Lysine

Lysine is a basic amino acid used in skincare as a humectant/skin-conditioning agent, typically at low concentrations, and it is generally well tolerated even on sensitive skin. As an endogenous building block, it has low inherent irritancy and patch-test reactions are uncommon, though stinging/irritation can occur in highly compromised barriers or when the overall formula pH is not skin-friendly. Given rare but possible reactivity in eczema-prone patients, it is best classified as very gentle rather than inert. Safety Notes: In commercial skincare, lysine is most often used as an amino-acid/NMF-supporting component or as part of an amino-acid blend, where it commonly appears at very low individual levels (about 0.01–0.3%) in leave-on moisturizers, serums, and some rinse-off cleansers. Higher-strength consumer products (e.g., barrier-repair creams, “amino acid complex” concentrates, and some exfoliating/actives formulas using lysine as a buffering/skin-conditioning amino acid) can reach multi-percent levels, with the upper end around ~5% in leave-on products before solubility, pH, sensory tackiness, and formula stability become limiting. No specific EU/FDA cosmetic maximum is set for lysine, so observed use levels are primarily constrained by formulation performance rather than regulation.

Lysine Carboxymethyl Cysteinate

Lysine Carboxymethyl Cysteinate is a water-soluble amino acid/thiol derivative primarily used as an antioxidant/conditioning agent, typically at low concentrations in leave-on formulas. Available safety and use-history data for similar amino-acid derivatives suggest low intrinsic irritation and minimal sensitization risk, though the cysteine/thiol functionality can rarely contribute to stinging in highly compromised skin. Given its generally gentle profile but non-zero potential in eczema/post-procedure barriers, a very gentle score is most consistent with patient safety. Safety Notes: In commercial skincare, Lysine Carboxymethyl Cysteinate is typically used as an antioxidant/anti-dark-spot supportive active (often within complex blends), with low-end usage around 0.05–0.2% in leave-on serums/creams where it functions as a secondary supporting ingredient. Higher-strength consumer-available brightening/anti-oxidative leave-on treatments have been observed around 0.5–2.0% when positioned as a primary active or key complex component; above ~2% is uncommon due to diminishing formulation practicality (odor/color, solubility, and stability constraints). Rinse-off products generally sit at the lower end because of reduced contact time and cost/performance tradeoffs.

Lysine HCL

MVP Approved - Lysine HCl is an amino acid ingredient used in skincare primarily for its hydrating effects with an ancillary anti-aging benefit, and it is generally well tolerated with very low irritancy risk.

Lysolecithin

Lysolecithin is a phospholipid-derived emulsifier and skin-conditioning agent typically used at low concentrations (about 0.1–2%) to support barrier-friendly formulations. Human patch-testing and clinical use suggest a low irritation profile for most users, but because it is a surfactant-like lipid that can increase penetration and occasionally sting on compromised/eczema-prone skin, it is not truly inert. Scoring it as very gentle (0.2) accounts for rare reactivity while remaining consistent with its generally good tolerability. Safety Notes: In commercial skincare, lysolecithin is most often used as a phospholipid co-emulsifier/solubilizer or liposome-supporting component at low levels (~0.05–0.5%) in leave-on lotions, serums, and toners, where it mainly aids dispersion and barrier feel rather than acting as a primary active. Higher consumer-available uses occur in phospholipid-rich barrier creams, cleansing balms/oils, and “liposomal/lamellar” systems where lysolecithin can be pushed into the ~1–5% range to build structure and improve stability/sensory, with higher levels limited by odor/color, tackiness, and potential irritation in leave-on products. No specific FDA/EU cosmetic maximum applies for lysolecithin; practical formulation constraints generally set the upper end in OTC products.

Macrocystis Pyrifera Extract

Macrocystis Pyrifera (giant kelp) extract is typically used at low concentrations as a humectant/skin-conditioning and antioxidant component, and is generally well-tolerated in routine patch-testing experience. However, as a marine botanical mixture (polysaccharides, proteins, trace minerals/iodine), it has a non-zero risk of irritant reactions or occasional sensitization in highly reactive or eczematous skin, especially when skin barrier is compromised. Given this predictable but low-level risk, it fits best as a gentle (not inert) ingredient. Safety Notes: In mass-market leave-on lotions/serums and rinse-off cleansers, Macrocystis pyrifera (kelp) extract is commonly used as a secondary botanical at very low levels (often ~0.01–0.1%) to support a marketing story and provide minor conditioning without impacting odor/color or stability. Higher-strength, consumer-available “seaweed/kelp” masks, body gels, and concentrated anti-cellulite/firming products can push total kelp extract to the low single digits, with the upper observed OTC end around ~5% when the extract is a major featured active (typically in leave-on gels/creams; rinse-off products rarely sustain the highest levels due to cost and sensorial constraints).

Madecassic Acid

Madecassic acid is a pentacyclic triterpene derived from Centella asiatica with documented anti-inflammatory and wound-healing properties, typically used at concentrations of 0.1-1%. Clinical studies and patch testing data consistently demonstrate excellent tolerability with minimal irritation potential, even in compromised skin barriers and post-procedure applications. While rare sensitivities can occur with any botanical derivative, the compound's anti-inflammatory mechanism actively counteracts irritation pathways, making it suitable for daily use in sensitive skin populations. Safety Notes: Madecassic acid, one of the pentacyclic triterpenes derived from Centella asiatica, appears in commercial skincare products across a wide range. At the lower end (0.001-0.01%), it's found in products containing Centella extract complexes where madecassic acid is one component among asiaticoside, asiatic acid, and madecassoside. High-strength specialized serums and targeted treatments marketed for scar reduction and skin repair contain isolated madecassic acid or concentrated triterpene blends at 0.1-1.0%, with some premium Korean and European formulations reaching the upper limit. These are predominantly leave-on products including serums, creams, and spot treatments.

Madecassoside

Madecassoside is a Centella asiatica-derived triterpenoid glycoside used primarily for anti-inflammatory, barrier-support, and soothing effects, typically at low concentrations (about 0.05–0.5%). In clinical use and patch testing, it is generally well tolerated and is often included in products for reactive or compromised skin, with irritation events being uncommon. Because botanical-derived actives can still trigger occasional idiosyncratic reactions in highly eczema-prone patients (especially in complex formulas), I score it as very gentle rather than exceptionally gentle. Safety Notes: In mass-market and dermocosmetic leave-on products, madecassoside is often used at very low levels (around 0.005–0.02%) as a supporting soothing/repair active alongside Centella extracts, and it also appears in some rinse-off cleansers at similarly low levels due to limited contact time. Clinical/technical use-levels and multiple commercial “Cica” balms/serums commonly sit around ~0.05–0.2% madecassoside, while a smaller set of consumer-available high-strength specialty formulations (typically leave-on creams/serums) push toward ~0.5% before solubility, cost, and sensorial/stability constraints become limiting. No specific global maximum is set for madecassoside in major cosmetics regulations, so the observed upper end is primarily constrained by formulation practicality rather than a hard legal cap.

Magnesium Aluminum Silicate

Magnesium aluminum silicate is an inert clay/mineral used primarily as a thickener, suspending agent, and opacifier, typically at low percentages in leave-on and rinse-off products. It has a very low rate of irritation in clinical use and patch testing, with most issues being rare mechanical dryness/tightness in highly compromised barriers rather than true chemical irritancy. Given its broad tolerability but acknowledging occasional reactivity in severely sensitive or eczema-prone skin, it fits best as exceptionally gentle rather than completely inert. Safety Notes: Magnesium aluminum silicate (a smectite-type clay/thickener) is used at very low levels (~0.05–0.3%) in emulsions and liquid cleansers as a suspending/viscosity aid, and more commonly around ~0.5–3% in lotions, creams, and masks for rheology and texture. The upper end is observed in consumer clay-based face masks, mud packs, and some mineral/powder or paste-style products where total clay structuring can reach ~10–15% while remaining OTC; leave-on masks/pastes tend to run higher than rinse-off cleansers due to desired body and oil-absorption.

Magnesium Ascorbyl Phosphate

Magnesium Ascorbyl Phosphate is a stable vitamin C derivative typically used around 1–10% in leave-on products, and it is generally better tolerated than low-pH L-ascorbic acid because it does not require an acidic formulation to function. Clinical and consumer data suggest low rates of stinging and erythema, but irritation can still occur in compromised barriers (eczema, post-procedure) or when layered with other actives, so it is best classified as gentle rather than very gentle. Safety Notes: In commercial products, Magnesium Ascorbyl Phosphate (a stable vitamin C derivative) is often used at very low levels (~0.05–0.5%) in multi-ingredient brightening moisturizers/cleansers where it serves as a supporting antioxidant and label claim component, with leave-on serums and lotions more commonly landing around 1–5% based on both market practice and published efficacy testing. High-strength consumer-available leave-on treatments and “vitamin C derivative” serums can reach 10% and, more rarely, ~15% MAP, typically requiring higher-pH aqueous gel/cream systems for solubility and stability; rinse-off formats generally sit toward the low end due to short contact time.

Magnesium Aspartate

Magnesium aspartate is a magnesium salt of an amino acid, typically used at low concentrations as a skin-conditioning/ionic supplement and is generally well tolerated in leave-on and rinse-off products. Available irritation and patch-test experience with magnesium and amino-acid salts suggests a low irritation profile, with occasional stinging possible on very compromised or fissured skin due to electrolyte load rather than true causticity. Given the limited dedicated topical clinical data and my focus on high-sensitivity populations, I rate it as very gentle but not completely inert. Safety Notes: Magnesium aspartate is an uncommon cosmetic magnesium salt, but when used it typically appears in multi-mineral/skin-conditioning blends and barrier-support creams at low levels around 0.01–0.2% as a trace electrolyte/conditioning agent. Higher-strength consumer products marketed for “magnesium skincare” (leave-on lotions/creams and some serums) can push magnesium salts into the ~1–3% range before solubility, crystallization, tackiness, and potential irritation become limiting; rinse-off formats generally stay toward the low end because contact time is short and electrolytes can destabilize surfactant systems.

Magnesium Carbonate

Magnesium carbonate is an inert, insoluble mineral powder used primarily as an absorbent/opacifier or anti-caking agent, typically at low percentages in cosmetics, and it is not a biologically active irritant in standard patch-testing contexts. However, as a fine particulate it can be mildly drying or mechanically irritating on compromised eczematous skin (especially in leave-on powders or high-load formulations), so I score it as very gentle rather than completely inert for patient safety. Safety Notes: In cosmetics, magnesium carbonate is used mainly as an absorbent/opacifying and slip/feel modifier in powders and some creams; at the low end it appears as a minor auxiliary (often with other fillers) in leave-on lotions/creams and occasional cleansers around ~0.05–0.5%. The highest consumer-available levels are found in anhydrous body powders, foot powders, and dry shampoos where magnesium carbonate can be a primary absorbent/filler, commonly 10–25% and observed up to ~35% in powder formats. There is no widely cited EU/FDA maximum specific to magnesium carbonate in cosmetics, so practical use is driven by sensory, dusting/whitening, and stability constraints, with much higher feasible loadings in dry (rinse-off/leave-on powder) products than in emulsions.

Magnesium Carboxymethyl Beta-Glucan

Magnesium carboxymethyl beta-glucan is a modified beta-glucan used as a soothing, barrier-supporting humectant/film former, typically at low concentrations (about 0.1–1%) in leave-on products. Beta-glucans and their derivatives are generally well tolerated in patch testing with low irritancy and are often included in formulas intended for compromised or sensitized skin. While true irritation is uncommon, any polymeric/metal-salt derivative can rarely provoke stinging on severely impaired barriers, so it is best classified as very gentle rather than completely inert. Safety Notes: In commercial skincare, magnesium carboxymethyl beta-glucan is most often used as a soothing/skin-repair polymer at low active levels (~0.01–0.1%) in mass-market leave-on creams/serums and in some rinse-off cleansers where deposition is limited. Higher-strength consumer-available “barrier repair” and post-procedure calming serums/ampoules and masks commonly run ~0.5–1.0%, with the highest OTC formulations observed around ~2% where viscosity/film-forming and cost become practical constraints. This ingredient is primarily found in leave-on products; rinse-off usage tends to stay toward the lower end due to performance and cost-in-use.

Magnesium Chloride

Magnesium chloride is primarily a humectant/mineral salt used in leave-on products (often ~0.5–5%) and much higher in “magnesium oil” sprays, where its high ionic strength can sting and feel burning on compromised skin. Clinically, concentrated salt solutions are well-known to cause transient irritation on eczema, fissures, and post-shave skin even without true allergy, so I score it as mild rather than gentle for patient safety. Safety Notes: In mainstream skincare, magnesium chloride is most often a minor electrolyte/mineral component or part of Dead Sea/mineral blends in toners, mists, lotions, and cleansers, where finished-product levels commonly start around ~0.05–1%. At the high end, consumer-available topical “magnesium oil” sprays/gels and mineral brines (leave-on body products) are formulated from concentrated MgCl2 solutions, with typical anhydrous-equivalent magnesium chloride levels roughly ~20–35% depending on hydration state and sensory limits. EU/FDA do not set a specific cosmetic maximum for magnesium chloride, so practical constraints are irritation potential, tackiness, and crystallization, with rinse-off products usually formulated lower than leave-on brines.

Magnesium Gluconate

Magnesium gluconate is a water-soluble magnesium salt primarily used as a skin-conditioning/mineral replenishing ingredient, typically at low concentrations, and it is generally well-tolerated in leave-on products. Clinical irritation and patch-test signals are uncommon compared with acids, surfactants, or fragrance allergens, but as an electrolyte salt it can occasionally sting compromised/barrier-impaired skin (e.g., eczema or post-procedure). Given sensitive-skin safety priorities, I rate it as very gentle rather than inert. Safety Notes: In commercial skincare, magnesium gluconate is most often used as a skin-conditioning/mineral-salt component in leave-on serums/creams and mineral/“electrolyte” mists at very low levels (around 0.01–0.1%), where it primarily supports marketing claims and mild conditioning without impacting texture. Higher-strength consumer products (typically leave-on gels/creams and some specialty “magnesium” body products) are observed up to about 3–5%, with practical limits driven by water solubility, tack/feel, and potential for stinging/irritation at elevated ionic strength; rinse-off formats usually sit toward the lower end because benefits are harder to substantiate with brief contact time.

Magnesium Hydroxide

Magnesium hydroxide is an inorganic base used mainly as a pH adjuster/buffering or absorbent; when present in leave-on products (often low percentages, but occasionally higher in deodorants), it can raise local pH and disrupt an already-compromised barrier. Clinical experience and patch testing show it is not a common allergen, but alkaline exposure can cause stinging, dryness, and irritant dermatitis in eczema-prone or freshly-shaved/occluded skin, so I rate it as mild rather than “very gentle.” Safety Notes: In consumer skincare, magnesium hydroxide appears at very low levels (~0.05–0.5%) as an alkalinity buffer/odor-adsorbing particulate in leave-on lotions, creams, and some acne/soothing products where pH control and sensory are limiting. Higher levels are found in OTC deodorant creams/sticks and “milk of magnesia”-inspired leave-on products, commonly ~5–15% and reaching ~20% in high-solids suspensions designed for strong odor control/mattifying effects. Use above a few percent is typically restricted to high-alkaline, particulate-rich systems and is more common in leave-on deodorant-type formats than in facial skincare; rinse-off cleansers generally sit on the low end due to viscosity, stability, and pH constraints.

Magnesium Laureth Sulfate

Magnesium laureth sulfate is an anionic surfactant used mainly in rinse-off cleansers (often a few percent up to ~10%+ active surfactant), and surfactants are a well-established cause of irritant contact dermatitis via lipid/protein disruption of the stratum corneum. While the magnesium salt and ethoxylation can make it somewhat milder than sodium lauryl sulfate, clinical experience and patch/usage data still show meaningful irritation risk in eczema-prone and highly sensitive skin—especially with frequent cleansing or compromised barriers. Given real-world cumulative exposure in routines and the population of reactive patients, I rate it as moderate with patch testing advised. Safety Notes: Magnesium laureth sulfate is primarily used as an anionic primary surfactant in rinse-off cleansers (shampoos, body washes, facial cleansers), where it can appear at low levels (~0.5–3%) as a secondary cleanser/foam booster alongside other surfactants or in very mild formulas. In mainstream rinse-off products it is commonly ~5–15% active, while high-foaming/high-cleansing consumer shampoos and clarifying washes can reach ~20–25% active surfactant load; leave-on products are uncommon and typically kept very low due to irritation potential.

Magnesium Oleth Sulfate

Magnesium oleth sulfate is an anionic surfactant/cleansing agent typically used in rinse-off cleansers where it can still disrupt the stratum corneum lipids and increase transepidermal water loss, a known pathway to stinging and eczema flares. Clinical experience and surfactant patch-testing literature consistently show sulfate-type anionics carry a moderate irritation risk, especially in compromised or atopic skin, even when formulated with milder co-surfactants. Given sensitive-skin populations and cumulative exposure from daily cleansing, a moderate score is warranted for patient safety. Safety Notes: Magnesium oleth sulfate is used primarily as a mild anionic surfactant in rinse-off cleansing systems; at the low end (~0.1–1%) it appears as a secondary/auxiliary surfactant or foam modifier in gentle facial cleansers and body washes. Mainstream rinse-off products commonly use it in the mid single-digits to low teens as part of the total surfactant blend, while high-foaming consumer-available shampoos/cleansers and sulfate-based cleansing concentrates can reach ~20–25% active as the primary surfactant component. It is rarely used in true leave-on skincare due to irritation/foam potential, so the practical market range is driven almost entirely by rinse-off formulations.

Magnesium Palmitoyl Glutamate

Magnesium Palmitoyl Glutamate is a fatty-acid amino-acid salt used mainly as a mild surfactant/emulsifier and skin-conditioning agent, typically at low concentrations in leave-on and rinse-off products. Available safety/patch-test experience for glutamate-based mild surfactants and fatty-acid salts suggests low inherent irritancy, with occasional stinging possible in highly compromised barriers (e.g., eczema flares) especially in cleanser systems. Given its generally good tolerability but non-zero risk in reactive skin when combined with other surfactants, a very gentle score is most consistent with patient-safety prioritization. Safety Notes: Magnesium Palmitoyl Glutamate is used commercially primarily as a lipid/amino-acid derived skin-conditioning/emollient and mild surfactant/texture aid, often appearing at low levels (~0.05–0.3%) in leave-on creams/lotions and some cleansers to support feel and formulation stability. In richer barrier creams, specialty moisturizers, and some anhydrous/lamellar systems it is marketed and used at higher levels around 1–2%, with the upper end of observed OTC consumer products reaching ~3% where it functions more materially as a structurant/skin-feel modifier; levels above this are uncommon due to diminishing sensory benefits and increased risk of waxy drag/instability, especially in leave-on emulsions.

Magnesium PCA

Magnesium PCA is a magnesium salt of pyrrolidone carboxylic acid used primarily as a humectant/skin-conditioning agent, typically at low percentages (about 0.1–3%) in leave-on products. Available patch-test and clinical use experience suggest a low incidence of irritation and sensitization, with reactions being uncommon and usually limited to highly compromised or very reactive skin. Given its generally good tolerability but acknowledging that salt forms can occasionally sting on barrier-impaired eczema skin, it fits best as very gentle rather than inert. Safety Notes: In commercial leave-on moisturizers, serums, and scalp tonics, Magnesium PCA is commonly used at low supportive levels (~0.05–0.5%) as part of an NMF/mineral-PCA complex for hydration and barrier support. Higher-strength consumer products marketed for oil-control, soothing, or “mineral PCA” claims (often alongside Zinc PCA and/or Sodium PCA) can reach ~1–3%, with the upper end around ~5% seen in some specialty OTC concentrates; above this, tackiness/solubility and overall electrolyte load typically limit practical use. Rinse-off cleansers and shampoos usually sit toward the low end (about 0.05–0.3%) due to cost and limited contact time.

Magnesium Stearate

Magnesium stearate is an inert fatty-acid salt used mainly as a lubricant/anti-caking agent and texture enhancer in powders, tablets, and some creams, typically at low percentages. Human patch testing and clinical experience generally show very low irritation potential, but it can occasionally contribute to dryness, friction-related irritation, or rare contact reactions in highly reactive/eczema-prone individuals, especially in leave-on powders. Given its overall benign profile but non-zero risk in compromised skin, it fits best as very gentle rather than completely inert. Safety Notes: Magnesium stearate is used primarily as a slip agent, anti-caking agent, binder, and texture modifier, and in skincare it most often appears in powders (setting powders, powder foundations), sticks (sunscreen sticks, deodorant/body balms), and some creams as a minor structurant. At the low end (~0.05–0.5%) it shows up as a flow aid/anti-caking agent in loose powders or as a minor processing aid in emulsions; at the high end, consumer-available anhydrous powders and pressed products can reach ~10–25% to optimize pressability, payoff, and feel (higher levels are uncommon outside powder/stick formats). It is not specifically concentration-restricted under EU/FDA cosmetic regulations, so the practical upper bound is set by product form (powder/stick) and sensory/processing constraints rather than legal limits.

Magnesium Sulfate

Magnesium sulfate (Epsom salt) is primarily a humectant/osmotic salt used in rinse-off soaks or low levels in leave-on formulas; as a high-ionic-strength ingredient it can sting and increase dryness, especially on compromised or eczematous skin. Clinical experience and patch/irritation testing generally show low sensitization risk, but irritation is possible at higher concentrations or on barrier-damaged skin, so it warrants a mild score for patient safety. Safety Notes: In consumer skincare, magnesium sulfate (Epsom salt) appears at very low levels (~0.01–0.5%) as an incidental/minor ionic adjuster or to support viscosity/texture in emulsions and masks, while still being listed on-pack. The highest observed OTC concentrations are in salt-based body scrubs, bath/shower exfoliating pastes, and rinse-off mud/salt masks where magnesium sulfate can function as the primary particulate/solids phase, commonly reaching ~10–25% in real-world products (higher is more typical for bath soaks, which are not always categorized as skincare leave-ons). Leave-on facial products are generally constrained to much lower levels due to tackiness, potential irritation/osmotic effects, and solubility/water-activity impacts, whereas rinse-off formats tolerate substantially higher loadings.

Magnolia Officinalis Bark Extract

Magnolia officinalis bark extract is used at low concentrations as an antioxidant/soothing, antimicrobial botanical (rich in honokiol/magnolol), but as a plant extract it contains multiple bioactive compounds that can trigger irritation or allergic contact dermatitis in reactive or eczematous skin. Clinical patch-test literature and real-world dermatology experience suggest generally good tolerability for most users, yet a meaningful minority of highly sensitive patients can react, especially in leave-on products or when combined with other actives. Given the unpredictability of botanical extracts and patient-safety considerations, it merits a mild irritancy score rather than being classified as “gentle.” Safety Notes: In mass-market leave-on creams/serums and many rinse-off cleansers, Magnolia officinalis bark extract is commonly dosed at low “botanical-support” levels around 0.01–0.1%, often as part of a broader soothing/antioxidant blend. Higher-strength consumer products positioned for anti-inflammatory/anti-acne or redness support (typically leave-on serums/spot products) use about 0.5–1.5%, with a practical OTC upper end around ~2% due to solubility, odor/color, and irritation/sensory constraints; magnolol/honokiol studies inform activity but most commercial products use the whole extract at these ranges rather than isolated actives.

Mahonia Aquifolium Root Extract

Mahonia aquifolium (Oregon grape) root extract is used for anti-inflammatory/antimicrobial and sebum-modulating benefits, typically at low percentages in leave-on products, but it contains isoquinoline alkaloids (e.g., berberine) that can be irritating on compromised skin. Human data and clinical experience suggest most users tolerate it, yet reactive or eczematous patients can experience stinging or contact dermatitis, especially when layered with other actives. Given the nontrivial sensitization/irritation potential of botanical extracts in highly sensitive populations, it warrants a mild-risk score. Safety Notes: In commercial leave-on skincare (calming/blemish, redness, and psoriasis-prone positioning), Mahonia aquifolium root extract is frequently used as a minor botanical active or supporting extract at ~0.01–0.2%, often within multi-extract blends and at the low end primarily for label/marketing and gentle skin-feel impact. Higher-strength OTC specialty products (not prescription/pro-only)—especially targeted serums/creams drawing on berberine/alkaloid activity—are seen around ~1–3%, with the upper end approaching ~5% when the extract is a primary featured active, constrained by color/odor, solubility, and potential irritation. Rinse-off products generally sit toward the lower portion of the range due to short contact time, while the highest levels are overwhelmingly in leave-on formats.