L'Oreal Professionnel Scalp Advanced 5-In-1 Professional Leave-In Serum

DESCRIPTION

What It Does: Provides transparent gel textures and thickening at very low concentrations via ph-responsive swelling.

Why It's Used: The most widely used gel thickener – provides crystal-clear, stable gels at concentrations as low as 0.1-0.5% with ph-controlled viscosity.

How It Works: Highly crosslinked polyacrylic acid remains tightly coiled at acidic ph. neutralization with naoh or triethanolamine ionizes carboxylic groups causing electrostatic repulsion that unfolds and swells the polymer coils, dramatically increasing viscosity. concentration-dependent thickening.

Typically Found In: Gels,serums,emulsions,sunscreens

TECHNICAL DETAILS

Primary Category: Functional ingredient – polyacrylic acid thickener

Secondary Functions: Skin conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 0.1%–2%

SOURCING & ETHICS

Vegan Status: Yes – synthetic

Halal Status: Yes

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Good safety profile at recommended concentrations. ewg score: 1–2.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Carbomer's ph-responsive swelling mechanism provides an elegant formulation control tool: a neutralized gel can be liquefied by ph reduction (adding acid) and re-thickened by reneutralization. this reversible rheology control allows two-phase products that mix on application without the need for mechanical emulsification.

Last Verified: Cosing database,cir safety assessment

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Provides the defining fresh citrus fragrance note alongside solvent and antimicrobial properties.

Why It's Used: The citrus industry's primary fragrance compound and the most abundant terpene in essential oils – limonene provides the clean, universally appealing fresh citrus scent character.

How It Works: D-limonene activates trpv1 mildly at high concentrations. antimicrobial via membrane disruption. solvent for oils and lipophilic compounds. cleaning via emulsification of lipid soils.

Typically Found In: Citrus-scented products,cleaning products,fragrance compounds

TECHNICAL DETAILS

Primary Category: Fragrance component – cyclic monoterpene

Secondary Functions: Skin conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 0.001%–3%

SOURCING & ETHICS

Vegan Status: Yes – from citrus peel essential oils

Halal Status: Yes

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Eu cosmetics regulation: declared fragrance allergen. oxidises to sensitising compounds (limonene hydroperoxides) on air exposure – use with antioxidant stabilisers. ifra guidelines apply.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Limonene's sensitisation risk arises not from limonene itself but from its autooxidation products (limonene-1,2-epoxide and limonene hydroperoxides) formed on air exposure. fresh limonene has low sensitisation potential, but air-oxidised limonene's hydroperoxide products are potent skin sensitisers. this explains why oxidation-stabilised formulations (with bht or other antioxidants) are required to manage limonene safety.

Last Verified: Cosing database,ifra standards,bråred christensson et al. limonene oxidation study

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Provides the most common natural floral-citrus fragrance note with additional anti-inflammatory properties.

Why It's Used: The most abundant fragrance terpene in nature – linalool forms the primary scent character of lavender, responsible for lavender's documented aromatherapy calming effects.

How It Works: Monoterpene alcohol activates gaba-a receptors for anti-anxiety activity (same receptor as benzodiazepines). inhibits glutamate-induced excitotoxicity. antimicrobial via membrane disruption. anti-inflammatory via nf-kb inhibition.

Typically Found In: Virtually all fragranced cosmetics

TECHNICAL DETAILS

Primary Category: Fragrance component – tertiary terpene alcohol

Secondary Functions: Skin conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 0.001%–3%

SOURCING & ETHICS

Vegan Status: Yes – from lavender, coriander, bergamot

Halal Status: Yes

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Eu cosmetics regulation: declared fragrance allergen on label when >0.001% (leave-on) or >0.01% (rinse-off). ifra guidelines apply.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Linalool's gaba-a receptor activation provides a pharmacological basis for lavender aromatherapy's documented anxiolytic effects. the same receptor modulation used by benzodiazepine drugs (such as diazepam) is activated by inhaled linalool vapor, providing receptor-mediated calming without the tolerance and dependence associated with pharmaceutical gaba-a modulators.

Last Verified: Cosing database,ifra standards,elisabetsky et al. linalool gaba study

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Activates trpm8 cold thermoreceptors for intense cooling sensation and analgesic activity.

Why It's Used: The most potent cosmetic cooling agent – direct trpm8 agonist providing cooling sensation without actual temperature reduction for refreshing and analgesic formulations.

How It Works: Potent trpm8 (menthol receptor/cold thermosensor) agonist – activation at room temperature mimics cold sensation without actual cooling. anti-pruritic via trpm8 activation competing with itch c-fiber signaling. antimicrobial via membrane disruption.

Typically Found In: Cooling products,scalp treatments,oral care,pain relief,foot care,after-sun

TECHNICAL DETAILS

Primary Category: Active ingredient – cooling sensory terpenoid

Secondary Functions: Redness reduction,anti-inflammatory,calming

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 0.1%–2%

SOURCING & ETHICS

Vegan Status: Yes – from mentha piperita or synthetic

Halal Status: Yes

Source Notes: Plant-derived extract or synthetic.

SKIN COMPATIBILITY

Irritancy Rating: 2/5 – low to moderate; potential sensitizer

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Non-irritating; ideal for reactive and sensitive skin.

Safe for Sensitive Skin: Avoid near eyes. use with caution at concentrations above 1% for sensitive skin.

SAFETY & COMPATIBILITY

Safety Profile: Eu max 4.5% (leave-on); regulations vary by application site. avoid on infants' face.

Works Well With: Ceramides,panthenol,allantoin,hyaluronic acid,centella asiatica

Avoid Combining With: No significant incompatibilities

SCIENTIFIC NOTE

Menthol's exceptional cooling potency stems from its ec50 for trpm8 activation of approximately 10μm (vs camphor's ec50 of ~5mm – 500× lower potency). this 500× potency advantage explains why even tiny concentrations of menthol provide intense cooling, while much higher concentrations of camphor are required for equivalent sensation.

Last Verified: Cosing database,mckemy et al. menthol trpm8 discovery,cir safety assessment

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Niacinamide strengthens the skin barrier, reduces visible pore size, regulates sebum production, fades dark spots, and improves skin texture and tone.

Why It's Used: It is used because it addresses multiple skin concerns at once without irritation, making it suitable for all skin types. it is stable in formulations and pairs well with most other actives.

How It Works: Niacinamide inhibits the transfer of melanosomes (pigment packets) to skin cells, reducing hyperpigmentation. it also stimulates ceramide synthesis to strengthen the skin barrier and reduces inflammation by modulating cytokine activity.

Typically Found In: Serums,moisturizers,toners,cleansers,eye creams,sunscreens,primers

TECHNICAL DETAILS

Primary Category: Active ingredient – vitamin

Secondary Functions: Barrier repair,brightening,anti-inflammatory

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 2%–10% (typical: 5%; higher concentrations may cause flushing in some individuals)

SOURCING & ETHICS

Vegan Status: Yes – synthetically produced

Halal Status: Yes – synthetic origin

Source Notes: Commercially produced via synthesis from nicotinic acid or 3-cyanopyridine. no animal-derived sources used in cosmetic-grade niacinamide.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low; concentrations above 10% may cause temporary flushing in sensitive individuals

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: At concentrations >10%, some users experience niacin flush (transient redness/tingling). generally very well-tolerated.

Safe for Sensitive Skin: Yes – one of the best-tolerated actives for sensitive skin

SAFETY & COMPATIBILITY

Safety Profile: Extensively studied and considered very safe. ewg hazard score: 1. no significant systemic toxicity concerns at topical concentrations.

Works Well With: Retinol,peptides,ahas/bhas,hyaluronic acid,ceramides,zinc,vitamin c,spf

Avoid Combining With: High concentrations of vitamin c (ascorbic acid) may theoretically convert to niacin – use at different times if using pure l-ascorbic acid above 15%

SCIENTIFIC NOTE

Niacinamide is a precursor to nad+ and nadp+, coenzymes vital to cellular energy metabolism. its benefits for dna repair and mitochondrial function make it a key ingredient in anti-aging strategies.

Last Verified: Cosing database,cir safety assessment,ewg skin deep,pubmed clinical studies

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Niacinamide strengthens the skin barrier, reduces visible pore size, regulates sebum production, fades dark spots, and improves skin texture and tone.

Why It's Used: It is used because it addresses multiple skin concerns at once without irritation, making it suitable for all skin types. it is stable in formulations and pairs well with most other actives.

How It Works: Niacinamide inhibits the transfer of melanosomes (pigment packets) to skin cells, reducing hyperpigmentation. it also stimulates ceramide synthesis to strengthen the skin barrier and reduces inflammation by modulating cytokine activity.

Typically Found In: Serums,moisturizers,toners,cleansers,eye creams,sunscreens,primers

TECHNICAL DETAILS

Primary Category: Active ingredient – vitamin

Secondary Functions: Barrier repair,brightening,anti-inflammatory

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 2%–10% (typical: 5%; higher concentrations may cause flushing in some individuals)

SOURCING & ETHICS

Vegan Status: Yes – synthetically produced

Halal Status: Yes – synthetic origin

Source Notes: Commercially produced via synthesis from nicotinic acid or 3-cyanopyridine. no animal-derived sources used in cosmetic-grade niacinamide.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low; concentrations above 10% may cause temporary flushing in sensitive individuals

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: At concentrations >10%, some users experience niacin flush (transient redness/tingling). generally very well-tolerated.

Safe for Sensitive Skin: Yes – one of the best-tolerated actives for sensitive skin

SAFETY & COMPATIBILITY

Safety Profile: Extensively studied and considered very safe. ewg hazard score: 1. no significant systemic toxicity concerns at topical concentrations.

Works Well With: Retinol,peptides,ahas/bhas,hyaluronic acid,ceramides,zinc,vitamin c,spf

Avoid Combining With: High concentrations of vitamin c (ascorbic acid) may theoretically convert to niacin – use at different times if using pure l-ascorbic acid above 15%

SCIENTIFIC NOTE

Niacinamide is a precursor to nad+ and nadp+, coenzymes vital to cellular energy metabolism. its benefits for dna repair and mitochondrial function make it a key ingredient in anti-aging strategies.

Last Verified: Cosing database,cir safety assessment,ewg skin deep,pubmed clinical studies

Primary Sources: 2026-03-12

DESCRIPTION

What It Does: Delivers characteristic cosmetic function at recommended use concentration.

Why It's Used: Selected for functional contribution and formulation compatibility supported by cosmetic science and regulatory safety data.

How It Works: Works through the mechanism of its molecular class as documented in peer-reviewed cosmetic literature.

Typically Found In: Skin care formulations

TECHNICAL DETAILS

Primary Category: Active ingredient – cosmetic active

Secondary Functions: Skin conditioning

Application Areas:

Facial Skincare

Body Care

Hair Care

Beard Care

Color Cosmetics (Makeup)

Dietary/Oral Supplements

Typical Concentration Range: 0.1%–10%

SOURCING & ETHICS

Vegan Status: Conditional

Halal Status: Yes

Source Notes: Commercially produced for cosmetic use. verify vegan/halal status with supplier.

SKIN COMPATIBILITY

Irritancy Rating: 1/5 – very low

Comedogenicity Rating: 0/5 – non-comedogenic

Sensitivity Concerns: Well-tolerated by most skin types.

Safe for Sensitive Skin: Yes

SAFETY & COMPATIBILITY

Safety Profile: Good safety profile at recommended concentrations. ewg score: 1–2.

Works Well With: Standard skincare actives

Avoid Combining With: No known significant incompatibilities

SCIENTIFIC NOTE

Triethanolamine has an established safety profile within the cosmetic regulatory framework at standard use concentrations.

Last Verified: Cosing database,triethanolamine technical literature

Primary Sources: 2026-03-12