New: our own Hairmetry line. Every ingredient explained
Hairmetry

Encyclopedia

Every molecule that touches your hair

From proven medicines to kitchen-cupboard oils, with the studies behind each one.

59 entries

1

  • other

    18-MEA (18-methyleicosanoic acid)

    The fatty acid on the outer surface of virgin hair that makes it water-repellent and smooth, lost with weathering and chemical treatment.

A

  • other

    Alcohol denat.

    Ordinary ethanol made undrinkable, a fast-drying solvent in hair sprays and gels that is not the same as the fatty alcohols in conditioners.

  • botanical

    Aloe vera

    Aloe gel is a soothing, water-binding scalp and hair conditioner, with no solid human trial showing it grows hair.

  • protein or peptide

    Amino acids

    Free amino acids in conditioners are small enough to enter hair, but there is little evidence that they strengthen it.

  • chemical treatment

    Ammonia and monoethanolamine (MEA)

    The alkaline agents that swell the cuticle so dye and bleach can enter; "ammonia-free" MEA dyes are not gentler.

  • oil or butter

    Argan oil

    A popular finishing oil for shine and anti-frizz, with only small lab studies behind it and no significant evidence for hair quality or growth.

  • oil or butter

    Avocado oil

    A rich oleic-acid oil common in deep conditioners, with no hair-fibre or clinical hair studies found.

B

  • oil or butter

    Batana oil

    Batana oil is a trending Honduran palm-nut oil sold for hair growth, with no peer-reviewed hair study found.

  • oil or butter

    Beeswax

    The classic hold-and-grip wax in pomades and braiding waxes; harmless for most people but a documented contact allergen for a minority.

  • conditioning agent

    Behentrimonium chloride

    A long-chain, positively charged conditioning ingredient that clings to hair and detangles it, with good lab evidence for smoothing and none for repair.

  • conditioning agent

    Behentrimonium methosulfate

    The methosulfate salt of the same C22 conditioning ingredient as behentrimonium chloride, slightly weaker in head-to-head lab testing.

  • conditioning agent

    Behenyl alcohol

    The longest common conditioner fatty alcohol, a stiff wax that gives rich, thick conditioners; it has no hair-specific studies.

  • bond builder

    Bis-aminopropyl diglycol dimaleate

    The active in Olaplex; it strengthens bleached hair in the lab, but the claim that it re-links broken disulfide bonds has never been independently confirmed.

C

  • oil or butter

    Castor oil

    Castor oil is a thick sealant that suits dry hair, but no controlled human trial shows it grows hair, and in rare cases it has matted a whole head of hair irreversibly.

  • other

    Ceramides

    Waxy lipids from the cement between hair cells; a lab study with ceramide-containing liposomes restored some lipids and break resistance, but retail products lack hair trials.

  • conditioning agent

    Cetearyl alcohol

    A waxy blend of cetyl and stearyl alcohols that thickens conditioners and builds the gel that carries the conditioning agent; despite the name, it is not a drying alcohol.

  • conditioning agent

    Cetrimonium chloride

    A shorter-chain conditioning ingredient, a bit less effective than the behentrimonium salts but lighter, found in many shampoos, light conditioners and sprays.

  • conditioning agent

    Cetyl alcohol

    A 16-carbon fatty alcohol that thickens conditioners and pairs with conditioning surfactants to form the gel; it is not a drying alcohol.

  • surfactant

    Cocamide MEA and cocamide DEA

    Foam boosters and thickeners in shampoo; the DEA type raises nitrosamine and allergy questions, which is why many brands moved to MEA or other thickeners.

  • surfactant

    Cocamidopropyl betaine

    The most common helper surfactant in shampoo, which makes sulfate cleansers gentler, thicker and foamier, and a rare cause of scalp allergy that usually comes from manufacturing impurities.

  • surfactant

    Coco-glucoside

    A coconut-derived mild cleanser that is a staple of sulfate-free shampoos, with the same contact-allergy caveat as decyl glucoside.

  • oil or butter

    Coconut oil

    The best-studied hair oil; in lab work it cut protein loss and fatigue damage when used before washing, but almost all studies come from coconut-oil sellers.

D

  • surfactant

    Decyl glucoside

    A plant-derived mild cleanser marketed as ultra-gentle, but its best-documented concern is a rising rate of contact allergy.

  • surfactant

    Disodium laureth sulfosuccinate

    A mild anionic cleanser often used as a secondary or co-primary surfactant that helps blends stay gentle while still cleaning.

E

  • oil or butter

    Emu oil

    Emu oil is a rendered bird-fat moisturizer with some mouse anti-inflammatory data, marketed for hair growth without any hair trial behind it.

G

  • humectant

    Glycerin

    A cheap water-binding ingredient in nearly every conditioner; no peer-reviewed hair study tests it, and the popular humidity rules are untested.

  • conditioning agent

    Guar hydroxypropyltrimonium chloride

    A plant-derived cationic polymer used in conditioning shampoos and "natural" conditioners to ease wet combing; it can build up on hair.

H

  • botanical

    Hibiscus

    Hibiscus leaf and flower extracts grew hair in rats and cultured rat follicles, but no human hair trial exists.

  • humectant

    Honey

    A sugar-rich natural humectant used in DIY and commercial masks; no hair-fibre study was found.

  • humectant

    Hyaluronic acid

    A large water-binding sugar molecule added to some leave-ins and masks; no hair-fibre study was found.

  • chemical treatment

    Hydrogen peroxide

    The oxidiser in every bleach and permanent dye; it lifts colour by destroying melanin but also oxidises the hair's own proteins, so damage rises with strength and repeat use.

  • protein or peptide

    Hydrolyzed silk

    Silk-derived peptides added for gloss and softness; the cosmetic safety panel judged most silk proteins safe, but there is no hair efficacy study.

I

  • drug with hair side effects

    Isotretinoin

    A prescription acne drug that causes shedding in a few percent of users and, far more seriously, severe birth defects.

J

  • oil or butter

    Jojoba oil

    A liquid wax often said to mimic scalp sebum; we found no hair-specific efficacy study.

K

  • bond builder

    K18 peptide (sh-Oligopeptide-78)

    A short cysteine-rich peptide modelled on hair keratin; inventor lab data look promising, but the one independent test found it acted mostly as a surface coating.

L

  • oil or butter

    Lanolin

    A sheep-wool wax used as an emollient in pomades and conditioners; a weak but real contact allergen whose true allergy rate is probably under-detected.

  • surfactant

    Lauryl glucoside

    A 12-carbon alkyl glucoside that foams a little better than decyl glucoside and carries the same class contact-allergy profile.

  • drug with hair side effects

    Lithium

    A mood-stabilising medicine whose label lists hair thinning, with figures ranging from no excess in trials to about 1 in 5 in older surveys.

M

  • oil or butter

    Mineral oil

    A cheap, non-penetrating hydrocarbon oil that coats hair for shine and slip but, unlike coconut oil, did not protect against protein loss in lab tests.

O

  • oil or butter

    Olive oil

    A traditional hair oil whose only supporting hair data is that its film thinned on hair like coconut oil did, suggesting some absorption.

P

  • humectant

    Panthenol

    A small vitamin B5 alcohol that enters the hair cortex and raised break stress in a lab study; the only humectant here with real hair-fibre data.

  • oil or butter

    Petrolatum

    A refined mineral-oil-and-wax jelly that is the base of many greasy pomades; it seals and adds shine but does not enter the hair.

  • conditioning agent

    Polyquaternium-10

    A positively charged cellulose polymer that coats hair during shampooing, easing wet combing and helping deliver silicones, with some build-up risk.

  • conditioning agent

    Polyquaternium-7

    A synthetic positively charged copolymer used in shampoos and rinse-offs to improve wet combing and feel.

  • humectant

    Propanediol

    A plant-derived glycol used as a humectant and solvent; no hair-specific study was found.

R

  • other

    Rice water

    Rice water is the starchy water left after soaking or boiling rice, a free and harmless rinse with no clinical hair study behind its growth claims.

S

  • oil or butter

    Shea butter

    A heavy plant butter widely used on coily hair, with no fibre-science data behind it.

  • surfactant

    Sodium cocoamphoacetate

    A mild two-charge helper surfactant used in baby, sulfate-free and sensitive-scalp shampoos to soften harsher cleansers.

  • surfactant

    Sodium cocoyl glutamate

    An amino-acid-based cleanser that was among the best-tolerated surfactants in a 105-patient patch-test study, with no scalp or hair trials yet.

  • surfactant

    Sodium cocoyl glycinate

    A glycine-based mild cleanser with one industry body-wash study showing mildness and no scalp or hair studies.

  • surfactant

    Sodium cocoyl isethionate

    A mild anionic cleanser, the basis of many syndet bars, with good lab evidence of being gentle on the skin barrier and growing use in sulfate-free shampoos and shampoo bars.

  • surfactant

    Sodium lauroamphoacetate

    The lauric-chain version of the amphoacetate family, used as a mild helper surfactant in sulfate-free shampoos.

  • surfactant

    Sodium lauroyl methyl isethionate

    A more soluble cousin of sodium cocoyl isethionate used as a mild cleanser in modern sulfate-free shampoos, with no independent studies of its own.

  • surfactant

    Sodium lauroyl sarcosinate

    An amino-acid-derived cleanser with good foam and cleaning power that is marketed as mild, though its mildness sits in the middle.

  • surfactant

    Sodium lauryl sulfate

    A cheap, strong cleanser and foamer that removes oil very well but is the most irritating common shampoo surfactant, so dermatologists use it as their standard test irritant.

  • humectant

    Sodium PCA

    A salt of an amino-acid derivative found in skin's natural moisturising factor, used as a humectant; no hair study was found.

  • conditioning agent

    Stearamidopropyl dimethylamine

    A conditioning agent that only becomes positively charged in acidic formulas, used in "quat-free" conditioners; no independent hair data were found.

  • conditioning agent

    Stearyl alcohol

    An 18-carbon fatty alcohol, a slightly heavier cousin of cetyl alcohol, used to thicken and soften conditioners; safe at cosmetic levels and rarely allergenic.

  • oil or butter

    Sunflower seed oil

    In the classic Marico study sunflower oil did nothing for protein loss, though later work suggests oils of its type can penetrate hair.