Alcohol denat. Worth avoiding
A short-chain drying alcohol used as a solvent and to speed drying. Harmless low on an ingredient list; in the first five of a leave-in it will leave hair dry and brittle over time.
Ingredient decoder
Ingredient decoder
What the words on the back of the bottle actually mean, and whether each one matters for your hair.
A
Amodimethicone Generally useful
A silicone that binds preferentially to damaged, more negatively charged areas of the shaft. Deposits where it is needed rather than uniformly, and builds up less than dimethicone.
Argan oil Generally useful
Mostly a surface oil — it seals and adds shine rather than penetrating. Excellent as a finishing layer on coarse or high porosity hair; too heavy on fine hair.
C
Coconut oil Depends on hair
One of the few oils small enough to penetrate the shaft and reduce protein loss during washing. Superb as a pre-wash treatment; on protein-sensitive or low porosity hair it can leave hair stiff.
D
Dimethicone Generally useful
A silicone that smooths the cuticle and cuts friction, which measurably reduces breakage during combing. Water-insoluble, so it needs a proper shampoo to remove — a build-up issue, not a health one.
G
Glycerin Depends on hair
A humectant that pulls water from the air. Superb in moderate humidity, counterproductive in very dry air (it pulls water out of the hair instead) and a frizz amplifier in very humid air.
H
Hydrolysed wheat protein Depends on hair
Small protein fragments that fill gaps in a porous cuticle and temporarily stiffen the strand. Genuinely useful on bleached hair; on healthy hair, repeated use makes it brittle.
K
Ketoconazole Generally useful
The most effective over-the-counter antifungal for dandruff and seborrhoeic dermatitis. Use twice weekly, left on the scalp for three to five minutes. Rotate with another active to keep it working.
P
Panthenol Generally useful
A humectant that penetrates the shaft and improves flexibility and moisture retention. One of the few ingredients that behaves well in almost every formula and on almost every hair type.
S
Sodium laureth sulfate Generally useful
The ethoxylated, gentler relative of SLS. Milder on skin, still an effective cleanser, and the workhorse of most decent shampoos. Fine for daily use on an oily scalp.
Sodium lauryl sulfate Depends on hair
A strong anionic surfactant. Cleans very effectively and lathers well; on dry, coarse or coloured hair it strips more lipid than most people want. Not linked to hair loss, despite the internet.
Z
Zinc pyrithione Generally useful
An antifungal that suppresses Malassezia. Reliable for maintenance dandruff control, gentler and slower than ketoconazole. Needs contact time on the scalp to do anything.
The verdicts here are about hair, not safety. "Worth avoiding" means we would not choose it for most hair in that position on a label — it does not mean an ingredient is dangerous.