Encyclopedia
Every molecule that touches your hair
From proven medicines to kitchen-cupboard oils, with the studies behind each one.
24 entries
A
-
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
Ammonium thioglycolate
The classic reducing agent in perms and thio relaxers; it breaks hair's disulfide bonds so the shape can change, with some loss each time.
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.
-
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.
-
supplement
Biotin
A B vitamin that restores hair only in the rare people who are deficient, and that can scramble thyroid and heart blood tests at the doses sold for hair.
-
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.
-
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
-
silicone
Dimethicone
The standard hair silicone, a water-insoluble oil that coats the fibre for slip, shine and friction control without repairing anything.
H
-
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 keratin
Keratin fragments, usually from wool or feathers, that coat damaged hair and in lab tests partly entered it and raised wet strength; the evidence is small and industry-linked.
-
protein or peptide
Hydrolyzed wheat protein
A common conditioner protein that raised dry strength of bleached and heat-damaged tresses in one lab test, with a small but real allergy risk.
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
-
supplement
L-cysteine
An amino acid that makes up much of hair keratin, with no controlled hair trial on its own.
M
-
bond builder
Maleic acid
A small, cheap acid with a reactive double bond that is the working part of Olaplex-type bond builders; evidence that it repairs bleached hair comes from patents and spectroscopy, not controlled trials.
O
-
protein or peptide
Oral keratin supplements
Keratin capsules with one small company-linked trial and no sign that swallowed keratin reaches your hair.
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.
-
chemical treatment
Persulfates (ammonium, potassium, sodium persulfate)
The booster salts in powder lighteners; they speed up bleaching and are a documented cause of occupational asthma and contact allergy in hairdressers.
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.
-
supplement
Silicon (orthosilicic acid)
A silicon supplement that improved strength and thickness of fine hair in one supplier-run trial.
-
chemical treatment
Sodium hydroxide and guanidine relaxers (lye and no-lye)
Chemical relaxers permanently straighten tightly curled hair; they work, but are linked to scalp burns, breakage and cancer associations still being investigated.