M–R

The science behind the ingredients in skincare.

M

Magnesium Ascorbyl Phosphate

Also known as: MAP
Type: Vitamin C derivative / antioxidant

A water-soluble derivative of ascorbic acid.

In skincare: Used in formulations targeting antioxidant protection, uneven pigmentation, and visible signs of skin aging.

Formulation note: Its stability and biological conversion differ from those of pure L-ascorbic acid.

Mandelic Acid

Type: Alpha hydroxy acid (AHA)

An aromatic alpha hydroxy acid derived from mandelates and naturally associated with bitter almonds.

In skincare: Used for exfoliation, texture refinement, uneven pigmentation, and blemish-prone skin.

Skin biology: Its relatively large molecular structure generally results in slower penetration than glycolic acid.

Marula Oil

INCI: Sclerocarya Birrea Seed Oil
Type: Botanical oil

A plant oil obtained from the seeds of the marula tree.

In skincare: Functions primarily as an emollient and skin-conditioning lipid.

Composition: Rich in oleic acid and containing other fatty acids and unsaponifiable components.

Meadowfoam Seed Oil

INCI: Limnanthes Alba Seed Oil
Type: Botanical oil

A stable vegetable oil obtained from meadowfoam seeds.

In skincare: Provides emollience, lubrication, and conditioning.

Formulation science: Its unusually high proportion of long-chain fatty acids contributes to its oxidative stability compared with many conventional plant oils.

Melatonin

Type: Indoleamine hormone

A hormone involved in regulation of circadian rhythms.

In skincare: Appears in some cosmetic formulations because of interest in its antioxidant and skin-protective properties.

Important distinction: Cosmetic topical use should not be equated with the systemic physiological role of endogenous melatonin.

Menthol

Type: Monoterpene alcohol

A naturally occurring compound found particularly in mint oils.

In skincare: Produces a characteristic cooling sensory effect through interaction with cold-sensitive sensory receptors.

Important consideration: The sensation of cooling does not necessarily mean that the skin itself has been physically cooled.

Methyl Gluceth-20

Type: Humectant / skin-conditioning agent

A polyethylene glycol ether derived from methyl glucose.

In skincare: Functions as a humectant and conditioning ingredient and can improve the sensory characteristics of moisturizers and cleansers.

Methylisothiazolinone

Type: Preservative

An antimicrobial preservative used to inhibit microbial growth in cosmetic formulations.

In skincare: Its primary purpose is product preservation, not direct skin treatment.

Important regulatory note: Its permitted cosmetic use is highly restricted in many jurisdictions because of its sensitization potential.

Mica

Type: Mineral / cosmetic pigment

A group of naturally occurring silicate minerals with characteristic layered structures.

In skincare: Used primarily for visual effects, opacity, shimmer, and optical modification in cosmetics.

Formulation use: Common in makeup, illuminating products, powders, and color cosmetics.

Mineral Oil

Also known as: Paraffinum Liquidum
Type: Highly refined petroleum-derived hydrocarbon mixture

A purified mixture of saturated hydrocarbons.

In skincare: Functions as an occlusive, emollient, and skin-protective ingredient.

Skin biology: Highly refined mineral oil can reduce transepidermal water loss by forming a hydrophobic film on the skin surface.

Important distinction: Cosmetic-grade mineral oil is highly purified and chemically distinct from crude petroleum.

Montmorillonite

Type: Smectite clay mineral

A layered silicate mineral capable of interacting strongly with water and various charged molecules.

In skincare: Used as an absorbent, thickening, and cleansing-support ingredient.

Formulation use: Common in masks and clay-based formulations.

N

Niacinamide

Also known as: Nicotinamide / vitamin B3
Type: Water-soluble vitamin

The amide form of vitamin B3.

In skincare: One of the most versatile cosmetic actives, associated with barrier support, reduction in the appearance of uneven pigmentation, regulation of visible oiliness, and improvement in overall skin appearance.

Skin biology: Niacinamide is a precursor to NAD and NADP, essential cellular cofactors involved in numerous metabolic and redox reactions.

Formulation note: Generally compatible with a broad range of cosmetic systems, although formulation pH and stability remain important.

N-Acetyl Glucosamine

Also known as: NAG
Type: Amino sugar

A naturally occurring monosaccharide derivative involved in biological glycosylation pathways.

In skincare: Used in formulations targeting hydration, skin conditioning, and uneven pigmentation.

Skin biology: N-acetylglucosamine is a building block involved in the synthesis of glycosaminoglycans and other glycoconjugates.

N-Acetyl Cysteine

Also known as: NAC
Type: Acetylated amino acid

A derivative of the sulfur-containing amino acid cysteine.

In biology: Serves as a precursor to cysteine and therefore contributes to glutathione synthesis.

In skincare: Investigated for antioxidant and skin-conditioning applications, although its topical cosmetic use is considerably less established than ingredients such as niacinamide or vitamin C.

Naringenin

Type: Flavonoid

A naturally occurring flavonoid found in citrus fruits and other botanical sources.

In skincare: Studied for its antioxidant and skin-conditioning potential.

Formulation note: Its poor water solubility can present delivery challenges.

Neuropeptides

Type: Signaling peptides

Peptides involved in communication between cells and the nervous and immune systems.

In skincare: Certain cosmetic peptides are investigated for effects related to skin appearance, sensory pathways, inflammation-related signaling, and expression lines.

Important distinction: Cosmetic peptide claims must be evaluated individually; "peptide" is a broad chemical category, not a guarantee of a particular biological effect.

O

Octocrylene

Type: Organic UV filter

An oil-soluble UV-absorbing ingredient.

In skincare: Used in sunscreen formulations to contribute primarily to UVB and short-wave UVA protection and to help stabilize certain other UV filters.

Formulation note: Its use is subject to regulatory requirements that vary by jurisdiction.

Oleic Acid

Type: Monounsaturated fatty acid / omega-9 fatty acid

A major fatty acid found in many plant oils.

In skincare: Functions as an emollient and lipid component.

Skin biology: Oleic acid can influence lipid organization and skin permeability. Its effects therefore depend strongly on concentration and formulation context.

Oat Lipids

Type: Botanical lipid fraction

Lipids isolated from oat kernels.

In skincare: Used for emollience, conditioning, and barrier-supportive formulations.

Composition: May contain triglycerides, phospholipids, ceramides, and other lipid components depending on the extraction process.

Oligopeptides

Type: Short-chain peptides

Molecules composed of relatively small numbers of amino acids.

In skincare: Used in targeted cosmetic formulations for skin conditioning and appearance-focused anti-aging strategies.

Formulation science: Peptide sequence, molecular size, concentration, stability, and delivery system determine biological relevance.

Panthenol

Also known as: D-Panthenol / provitamin B5
Type: Humectant / vitamin precursor

An alcohol analogue of pantothenic acid.

In skincare: Provides humectant, conditioning, and soothing properties.

Skin biology: Once converted to pantothenic acid, it contributes to pathways associated with coenzyme A metabolism.

P

Palmitic Acid

Type: Saturated fatty acid

A common long-chain fatty acid found in skin lipids and numerous plant and animal-derived materials.

In skincare: Functions as an emollient, consistency agent, and formulation lipid.

Skin biology: Fatty acids including palmitic acid contribute to the lipid environment of the stratum corneum.

Palmitoyl Tripeptide-1

Type: Lipopeptide

A peptide linked to a palmitoyl fatty-acid chain to increase its compatibility with lipid-containing formulations.

In skincare: Used in formulations targeting the appearance of fine lines, firmness, and skin conditioning.

Formulation science: The lipid portion can influence partitioning and interaction with the skin's surface.

Palmitoyl Tetrapeptide-7

Type: Lipopeptide

A synthetic peptide linked to palmitic acid.

In skincare: Commonly used in anti-aging formulations focused on skin conditioning and the appearance of firmness and fine lines.

Peptides

Type: Short chains of amino acids

Peptides are molecules composed of linked amino acids.

In skincare: Cosmetic peptides are used in numerous strategies targeting firmness, elasticity, fine lines, barrier function, pigmentation, and overall skin conditioning.

Skin biology: Their activity depends on sequence, structure, stability, receptor or enzyme interactions, concentration, and delivery.

Important distinction: Not every ingredient described as a peptide has the same biological mechanism.

Phenoxyethanol

Type: Preservative / aromatic ether alcohol

A widely used antimicrobial preservative.

In skincare: Primarily protects water-containing formulations against microbial contamination.

Formulation note: Often combined with other preservation technologies to provide broad-spectrum protection.

Phospholipids

Type: Amphiphilic lipids

Lipids containing both hydrophilic and hydrophobic regions.

In skin: Fundamental components of biological membranes and important participants in lipid organization.

In skincare: Used as emulsifiers, conditioning agents, delivery-system components, and biomimetic formulation materials.

Phytosphingosine

Type: Sphingoid base / skin lipid component

A naturally occurring lipid-related molecule found in the stratum corneum.

In skincare: Used in barrier-supportive and skin-conditioning formulations.

Skin biology: Sphingoid bases are closely related to the metabolism and organization of ceramides and other epidermal lipids.

Polyglutamic Acid

Type: Polypeptide / biopolymer

A polymer composed of glutamic-acid units, commonly produced through microbial fermentation.

In skincare: Used primarily as a film-forming and water-binding ingredient.

Formulation benefit: Can create a hydrated, smooth surface feel and complement conventional humectant systems.

Polysorbate 20

Type: Nonionic surfactant / solubilizer

A surfactant derived from sorbitan and lauric acid with polyoxyethylene chains.

In skincare: Helps solubilize fragrances and oil-soluble materials in water-based formulations.

Propanediol

Type: Diol / humectant / solvent

A multifunctional ingredient used in water-based cosmetic formulations.

In skincare: Provides humectancy, solvent activity, and improved sensory properties.

Formulation benefit: Can assist with dissolution and delivery of certain cosmetic ingredients.

Propylene Glycol

Type: Diol / humectant / solvent

A small multifunctional organic compound widely used in cosmetics.

In skincare: Functions as a humectant, solvent, and formulation aid.

Important distinction: Although chemically an alcohol, propylene glycol behaves very differently from volatile ethanol.

Q

Quercetin

Type: Flavonoid polyphenol

A naturally occurring plant flavonoid found in numerous fruits, vegetables, and botanical materials.

In skincare: Studied primarily for its antioxidant and skin-conditioning potential.

Formulation challenge: Its low water solubility can require specialized delivery approaches.

Quinoa Extract

INCI varies by preparation
Type: Botanical extract

An extract derived from Chenopodium quinoa.

In skincare: Used primarily for skin conditioning and antioxidant-oriented formulations.

Composition: Depending on extraction, quinoa-derived materials may contain peptides, amino acids, polysaccharides, minerals, and phenolic compounds.

R

Retinal

Also known as: Retinaldehyde
Type: Retinoid / vitamin A aldehyde

A naturally occurring retinoid and metabolic intermediate in the conversion of vitamin A derivatives.

In skincare: Used in formulations targeting fine lines, uneven texture, and signs of photoaging.

Skin biology: Retinal can be converted enzymatically to retinoic acid, the biologically active retinoid responsible for many retinoid signaling effects.

Formulation note: Stability is a major consideration because retinal is sensitive to environmental conditions.

Retinol

Type: Retinoid / vitamin A alcohol

A form of vitamin A widely used in cosmetic skincare.

In skincare: Used to improve the appearance of fine lines, uneven texture, and pigmentation.

Skin biology: Retinol undergoes enzymatic conversion first to retinal and subsequently to retinoic acid.

Formulation challenge: Retinol is sensitive to oxidation, light, and heat, making packaging and formulation architecture important.

Retinyl Palmitate

Type: Retinoid ester

An ester formed from retinol and palmitic acid.

In skincare: Used as a relatively stable vitamin A derivative in cosmetic formulations.

Skin biology: It requires enzymatic conversion through retinol and retinal before reaching retinoic acid.

Important distinction: Retinyl palmitate is not biologically equivalent to retinoic acid and generally has a different potency profile.

Resveratrol

Type: Stilbene polyphenol

A naturally occurring polyphenolic compound found in certain plants, including grape skins.

In skincare: Used primarily for antioxidant and skin-conditioning applications.

Formulation note: Solubility, oxidation, light sensitivity, and delivery can influence its practical performance.

Rice Bran Oil

INCI: Oryza Sativa Bran Oil
Type: Botanical oil

An oil extracted from rice bran.

In skincare: Functions as an emollient and skin-conditioning lipid.

Composition: Contains fatty acids as well as unsaponifiable compounds such as phytosterols and tocopherol-related antioxidants.

Rosehip Seed Oil

INCI: Rosa Canina Seed Oil / Rosa Rubiginosa Seed Oil, depending on source
Type: Botanical oil

A seed oil obtained from species of Rosa.

In skincare: Provides emollience and skin conditioning.

Composition: Often rich in linoleic and alpha-linolenic acids, with composition varying by species, cultivation, and processing.

Rosemary Leaf Extract

INCI: Rosmarinus Officinalis Leaf Extract / Salvia Rosmarinus Leaf Extract
Type: Botanical antioxidant extract

An extract derived from rosemary leaves.

In skincare: Used for antioxidant and skin-conditioning purposes and can also help protect certain formulations against oxidative deterioration.

Composition: Depending on extraction, may contain phenolic compounds such as rosmarinic acid and carnosic-acid-related constituents.

Rose Water

Common INCI: Rosa Damascena Flower Water
Type: Botanical floral water

A water-based aromatic distillate produced during the processing of rose flowers.

In skincare: Primarily functions as a fragrance, skin-conditioning, and sensory ingredient.

Important distinction: The biological activity of a floral water is not equivalent to that of a concentrated botanical extract or essential oil.