"Sulfate-free" is everywhere, from pharmacy shelves to TikTok routines, to the point of becoming a buying reflex. But as so often in cosmetics, reality is more nuanced than the slogan: not all sulfates are equal, and a "sulfate-free" shampoo is not automatically gentle. Here is what you really need to know before clearing out your bathroom.
What are sulfates for in a shampoo?
Sulfates are surfactants: molecules with one end that grabs water and another that grabs oil. That is what lets a shampoo lift sebum, styling product residue and pollution, then carry it all away when you rinse. They are also what produces the abundant lather that many people wrongly equate with effective cleansing.
Without a surfactant, there is no shampoo. So the real question is not "sulfate or no sulfate", but which surfactant, at what dose, and surrounded by what.
Why sulfates have a bad reputation
Two names attract most of the criticism: Sodium Lauryl Sulfate (SLS) and Sodium Laureth Sulfate (SLES). Highly effective and very cheap, they are used massively in conventional shampoos. Their high detergent power can:
- strip the hydrolipidic film that protects the scalp, leading to tightness, itching or a feeling of dryness in sensitive people;
- open the cuticle and speed up the fading of colour;
- dry out already fragile lengths, particularly curly, coily or damaged hair;
- prematurely remove treatments deposited on the fibre, such as a keratin treatment or a straightening service.
To that you can add a manufacturing point: SLES is obtained by ethoxylation, a chemical process that natural cosmetic standards such as COSMOS exclude.
Not all sulfates are equal
This is the crux of the matter, and what "sulfate-free" marketing keeps quiet about. Between a petrochemical SLES and a Sodium Coco-Sulfate derived from coconut oil, there is a world of difference:
- Sodium Coco-Sulfate (SCS) is made from coconut fatty acids, without ethoxylation. Its larger molecule penetrates the skin less than SLS, which makes it better tolerated. That is why it is accepted by COSMOS NATURAL and COSMOS ORGANIC certification, while SLS and SLES are not;
- above all, a surfactant never works alone. SCS combined with gentle surfactants (glucosides, glutamates) gives a far gentler cleansing base than the same SCS used alone and overdosed.
In other words: a naturally certified shampoo containing well-supported Sodium Coco-Sulfate can be gentler than a "sulfate-free" shampoo packed with harsh surfactants from another family. The claim alone tells you nothing; it is the full formula that counts.
Who genuinely benefits from avoiding strong sulfates?
- Sensitive, reactive or itch-prone scalps: the first group concerned. Switching to a gentle cleansing base often changes things within a few weeks.
- Coloured hair: powerful detergents speed up pigment fading. A gentle base makes colour last longer.
- After a keratin or Brazilian straightening treatment: salons systematically recommend a gentle shampoo, or the result disappears within a few weeks. We go into this in our comparison of Brazilian straightening, keratin straightening and keratin haircare.
- Dry, curly, coily hair: these hair types produce less sebum along the fibre and cope badly with repeated stripping.
- Very frequent washing: the more often you wash, the more the gentleness of the cleansing base matters.
The gentle surfactants to spot on a label
On the INCI list, look for these families near the top:
- the glucosides: Lauryl Glucoside, Coco-Glucoside, Decyl Glucoside, derived from sugar and coconut;
- the glutamates: Sodium Cocoyl Glutamate, Disodium Cocoyl Glutamate, derived from amino acids;
- the betaines: Cocamidopropyl Betaine, often used as a secondary surfactant;
- the isethionates and taurates: Sodium Cocoyl Isethionate, Sodium Methyl Cocoyl Taurate.
A useful reminder: the INCI list is ordered by decreasing concentration. The first two or three surfactants named give the cleansing base its real personality. To learn how to decode the rest of the label, silicones and PEGs included, we have written a full guide: how to read a shampoo label.
So where does KERA NEXT stand?
Full transparency, exactly as on our product pages: the Keratin Volume Boost Shampoo is not "sulfate-free" in the strict sense. Its cleansing base opens with Lauryl Glucoside, a gentle surfactant derived from sugar and coconut, backed up by Sodium Coco-Sulfate and gentle glutamates. Zero SLS, zero SLES, zero silicone, zero PEG, and a formula certified COSMOS NATURAL by ECOCERT Greenlife.
It is a deliberate choice: this combination genuinely cleanses, lathers pleasantly and stays gentle on the scalp, where some 100% glucoside formulas struggle to wash hair that tends to get greasy. The full INCI list is published on the product page, so you can check every ingredient.
In summary
- "Sulfate-free" is neither a guarantee of gentleness nor a must for everyone.
- The sulfates to avoid first are SLS and SLES; Sodium Coco-Sulfate, accepted in certified cosmetics, is in another category.
- What matters: the first surfactants on the INCI list and the overall balance of the formula.
- Sensitive scalp, coloured hair, recent straightening or very dry hair: go for gentle cleansing bases, with or without the marketing claim.