Dye your hair and sooner or later someone will tell you to switch to a sulfate-free shampoo. A quick note on spelling: "sulphate" is the traditional British spelling of exactly the same word, while "sulfate" is the form printed on ingredient lists. I'll use "sulfate" throughout so you can match it to the back of the bottle.

Sulfate-free shampoo for colour-treated hair is a sensible choice, but not a guarantee. Sulfates are strong cleansers that can help wash dye out, yet the evidence that sulfate-free formulas keep colour noticeably longer is thin. Wash temperature, how often you wash and sun exposure matter just as much.

Below: what the research does and doesn't show, how to read a label, seven UK shampoos with honest trade-offs, and routine changes that work whatever you buy.

Does sulfate-free shampoo really protect hair colour?

Possibly a little, and nobody has proved by how much. Salons and brands repeat the advice constantly, so I went looking for a controlled, peer-reviewed trial comparing sulfate and sulfate-free shampoos on dyed hair. I couldn't find one. What I did find is a handful of smaller pieces of evidence:

• A lab test that found no difference. The Beauty Brains, a site run by cosmetic chemists, tested sulfate-free against sulfate-containing shampoos on dyed hair and reported no difference in colour fade (2014 post). It's a small, unreviewed test, so treat it as a signal rather than a verdict.
• Every surfactant moves some dye. A 2009 paper in the Journal of Cosmetic Science (Zhou and colleagues) found that surfactants increase dye loss from dyed hair by helping water into the fibre. Sodium laureth sulfate raised dye dissolution by 47% for dark brown hair after an hour. A cationic conditioning ingredient, cetrimonium chloride, raised it by 127%.
• Sun plus shampooing is the worst combination. A 2005 study by Locke and Jachowicz in the Journal of Cosmetic Science found fading was greatest when dyed hair was both irradiated and shampooed. Removing UV altogether cut photofading by 27% to 63%, depending on the dose.

So sulfates do carry some dye away, but they aren't uniquely guilty. A sulfate-free shampoo is a low-risk step, particularly if your scalp is sensitive or your hair is dry. It just shouldn't be the only thing you change.

What are sodium lauryl sulfate and sodium laureth sulfate?

They're surfactants, the cleaning agents in most shampoos. One end of the molecule clings to water and the other grabs oil, so sebum, sweat and styling products get lifted off and rinsed away. They also produce the thick lather many of us associate with "clean".

The three you'll meet most are sodium lauryl sulfate (SLS), sodium laureth sulfate (SLES) and ammonium lauryl sulfate. SLES is a modified version of SLS and is generally regarded as the milder of the two. Both are cheap and effective, which is why they've dominated shampoo for decades.

Are they dangerous? The Cosmetic Ingredient Review panel concluded in its 1983 report that SLS and ammonium lauryl sulfate appear safe in products designed for brief use followed by thorough rinsing, which describes a shampoo. The practical problem is irritation: some people with dry or sensitive scalps find them harsh. Our sulphate-free shampoo UK explainer goes deeper on that side of things.

How do you spot sulfates on a shampoo label?

Ignore the front of the bottle and read the ingredient list, which runs from highest concentration to lowest. Cleansers sit near the top, so check the first five or six names. Anything that ends in "sulfate" is one:

• Sodium lauryl sulfate (SLS)
• Sodium laureth sulfate (SLES)
• Ammonium lauryl sulfate
• Ammonium laureth sulfate

Sulfate-free shampoos typically swap in cleansers such as sodium cocoyl isethionate, sodium lauroyl methyl isethionate or cocamidopropyl betaine. They tend to lather more softly, which can feel odd at first. If you'd like a wider shortlist beyond coloured hair, our guide to the best sulphate-free shampoo in the UK covers it.

Is sulfate-free shampoo automatically gentle?

No, and this is where marketing runs ahead of chemistry. Three things to watch:

• Sulfonates aren't sulfates. Sodium C14-16 olefin sulfonate isn't a sulfate, so a shampoo containing it can legitimately say "sulfate-free". It's still a strong degreaser, and some people find it drying. Evidence here is mostly ingredient-database commentary rather than trials, so take it as a caution rather than a rule.
• "SLS-free" isn't "sulfate-free". A bottle can leave out SLS and still contain another sulfate. Aveda's Color Conserve is a good example: Liberty London's listing shows ammonium lauryl sulfate in the ingredients. Plenty of people like it, but it's one to avoid if you want a strictly sulfate-free routine.
• The rest of the formula counts. As the cetrimonium chloride result above suggests, conditioning ingredients can move dye too. The cleanser is one variable among several.

Best sulfate-free shampoos for colour-treated hair in the UK

These are options I could verify from UK retailer or brand listings. I haven't tested them against each other, so the trade-offs come from the listings, not from lab results. Prices and formulations change and retailers discount constantly, so I've only given a figure where I saw a listed price, and otherwise described the tier. Everything here was checked in October 2026 — worth re-reading the ingredient list on the bottle you actually buy.

And the honest trade-off for each:

• Olaplex No.4: sold on bond repair rather than colour retention, so you may be paying for technology a simple colour routine doesn't need. I haven't seen independent evidence that it extends colour.
• Pureology Hydrate: priced as a salon product, and the standard Hydrate is aimed at dry hair. Lookfantastic lists a separate Sheer version for fine, dry hair.
• Kérastase: the highest list price here. The refill pouch is the useful part if packaging matters to you.
• L'Oréal Professionnel: the Vitamino Color range has several shampoos, and Spectrum is the one listed as sulphate free, so check which you pick up. Its "100 days" colour claim is the brand's own and refers to the full routine.
• Maria Nila: I only found it through its own UK store and specialist stockists, so it's harder to grab on a whim.
• Herbal Essences: a straightforward cleanser rather than a treatment. Ranges change, so read the ingredients before buying.
• Aveda: fine for many people, but it isn't sulfate-free, so it doesn't fit this guide's brief.

If packaging matters as much as ingredients, our look at the best refillable shampoo in the UK compares the refill options.

What else keeps hair colour from fading?

Quite a lot, and none of it depends on which bottle you buy:

1. Wash less often. L'Oréal Professionnel's UK advice is two to three times a week. That's brand guidance, but it fits the lab picture: each wash moves a little dye.
2. Use cooler water. Stylists and hairdressing brands say hot water lifts the cuticle and lets colour escape. I couldn't find a controlled study, so call it sensible rather than proven. It costs nothing to try lukewarm.
3. Shield your hair from sun. The Locke and Jachowicz work above shows UV is a real driver of fade. A hat or a UV-protecting leave-in is the practical fix.
4. Use a heat protectant. Hairdressing brands recommend it for colour longevity. Again, I found advice rather than trials, but it protects the hair itself either way.

Honestly, if you only do the first two, you'll probably see more difference than from switching shampoo alone.

Frequently Asked Questions

Is sulphate free shampoo the same as sulfate free shampoo?

Yes. "Sulphate" is the British spelling and "sulfate" the American and chemical one. They describe the same ingredients, and ingredient lists use "sulfate", so that's the spelling to look for on a label.

Does sulfate free shampoo stop colour fading?

Not on its own. Colour fades through washing, hot water, sun and heat, and the one lab test I found comparing sulfate and sulfate-free shampoos reported no difference in fade. It may help if sulfates dry or irritate your scalp, but the evidence is thin.

What shampoo is best for coloured hair in the UK?

There's no single best. Look for a sulfate-free formula suited to your hair type, such as one for dry, fine or damaged hair, and check the ingredient list rather than the front label. The table above lists UK options at different price points.

Is sodium laureth sulfate bad for dyed hair?

There's no strong evidence it is uniquely bad. In a 2009 lab study, SLES raised dye loss by 47% after an hour's soaking, but a conditioning ingredient raised it by 127%. If your scalp is sensitive or your hair is dry, a milder cleanser may simply feel better.

Is olefin sulfonate a sulfate?

No, it's a sulfonate, a different chemical group, so a shampoo with sodium C14-16 olefin sulfonate can still be labelled sulfate-free. It's a strong cleanser, though, and some people find it drying.

How can I tell if a shampoo is sulfate-free?

Read the ingredient list for anything ending in "sulfate", such as sodium lauryl sulfate, sodium laureth sulfate or ammonium lauryl sulfate. A front label saying "SLS-free" doesn't rule out other sulfates.

How often should I wash colour-treated hair?

L'Oréal Professionnel's UK guidance is two to three times a week to slow fading. Your scalp matters too, so stretch the gap gradually rather than leaving an oily scalp for days.

One last thing, since you're here for a better shampoo routine. Lifelong's REEFill line (hand soap, body wash and shampoo) launches on Kickstarter in March 2027. The containers are 100% ocean-bound recycled plastic, and the natural powder refills arrive in plastic-free compostable pouches. Early-bird sign-up gets you 40% off.