Sulphate Free Shampoo For Colour Treated Hair, Does It Actually Protect Your Colour?

Everyone tells you the same thing after a colour appointment. Sulphate free from now on, or you will wash your money down the drain.

It is repeated so consistently that it feels like settled science. It is not. Cosmetic chemists have pointed out for years that no published studies validate the idea that sulphates fade colour faster than other surfactants, and more recent lab testing has found sulphate shampoos performing as well as sulphate free ones on colour retention.

Here is where the rule came from, what the evidence actually supports, and the things that make a far bigger difference to how long your colour lasts.

Where The Rule Came From

Worth knowing the history, because it explains a lot.

Sulphate free positioning for coloured hair began as one brand's marketing angle. It worked extremely well, other brands adopted it, and within a few years it had hardened into common knowledge. Before that, sulphate free was not something people sought out, including for coloured hair.

That does not automatically make it wrong. Plenty of marketing claims turn out to be true. But a claim that spread through repetition rather than through evidence deserves a second look, especially when it is costing you money every wash.

What The Evidence Actually Says

The Experts Do Not Agree

Here is something the shopping lists never tell you. Ask two dermatologists and you get two answers.

One position, stated confidently across beauty media, is that sulphate free is non negotiable for coloured hair because milder surfactants cleanse without dulling pigment. The other, argued just as confidently, is that for colour treated hair you can use either type because the sulphate question does not have a big impact on colour preservation. Plenty of professional sources still recommend sulphate free, so this is a live disagreement rather than a settled overturning.

When expert opinion splits like that, the honest conclusion is that the effect is small enough to be arguable. Genuinely large effects do not produce this kind of disagreement.

The Label Cannot Tell You What You Need To Know

The deeper problem is that sulphate free describes what is absent rather than how a formula behaves. Formulation references are consistent that cleansing depends on the total surfactant level and the balance of primary and secondary surfactants, not on one ingredient class. A sulphate shampoo at low concentration with good conditioning agents can behave very differently from a sulphate free one built around a strong alternative.

What about colour safe as a label instead? It is more useful in spirit, since it at least points at performance rather than absence. Be aware though that it is a marketing term with no universal regulatory definition behind it, so it is a better question to ask a brand rather than a guarantee to trust on a bottle.

What Actually Fades Your Colour

These are the levers that move, ordered by how well the evidence actually supports them.

Notice where the sulphate question sits. Bottom of the list, and the only entry anybody argues about.

The Sun Is Doing More Than Your Shampoo

This is the finding worth acting on. Experimental work has repeatedly shown that ultraviolet light photodegrades artificial hair colour, and a 2023 study on sun exposure and permanently dyed hair measured the effect directly. Dyed hair left in sunlight fades more than hair exposed to washing alone.

Which is quite something, given how much of the conversation is about shampoo and how little of it is about the fact that you live in Australia.

Porosity Is The Other Big One

Colour processed hair is more porous by definition, because lifting the cuticle is how the colour got in. Research on hair porosity and dyeing confirms that higher porosity means stronger dye uptake, and damaged or missing cuticle scales let more dye through in both directions.

That is why the same colour on two people fades at different rates, and why treating the condition of your hair often does more for colour longevity than any change of shampoo.

[tip-text="If you are outdoors a lot, a hat is doing more for your colour than any shampoo on your shelf. Unglamorous, free, and the best evidenced step available."]

So Should You Use It Or Not?

Yes, if it suits your hair and your scalp. No, if you are only using it because someone told you coloured hair requires it.

The people with the strongest case for milder cleansing are those with sensitive, eczema prone or allergy prone scalps, and those with dry, coarse or curly hair. If you fit that description and you also colour your hair, sulphate free is a sensible choice for reasons that have nothing to do with pigment.

You Do Not Have To Pick A Side

The most practical approach, and one almost nobody mentions, is to use both.

• Use a gentler shampoo for your regular washes.

• Use something stronger occasionally, when buildup has flattened your colour and dulled your shine.

• Judge the result by how your colour looks after a fortnight, not by what the bottle claims.

This suits people with coloured hair and an oily scalp particularly well, since they are otherwise stuck choosing between their colour and a clean scalp. They are not actually in conflict. Worth knowing too that colour safe clarifying formulas exist, and removing buildup can make colour look brighter rather than duller, so the occasional deep cleanse is not the enemy it is made out to be.

The Week After Your Appointment

This part genuinely does matter, and it gets far less attention than the shampoo debate.

• Leave it as long as you comfortably can before the first wash. Work on how readily hair dyes desorb indicates the earliest washes carry away the most colour, largely because loosely held dye sits near the surface at first.

• Keep that first wash brief and gentle.

• Hold off on a deep clarifying wash for the first week. Save it for when buildup is genuinely the problem.

• Get a treatment in early rather than waiting until the colour looks tired.

• If you swim, wet your hair first and rinse straight after. Clinical guidance on chlorine and hair is clear that colour treated hair is more vulnerable, and that rinsing before and after genuinely reduces the damage.

Do those five things and you will get more from your colour than switching cleansers will ever give you.

What The Research Actually Shows

• UV fading is the best evidenced factor by far. Multiple experimental studies, measurable effects, and it outranks anything happening in your shower.

• Porosity genuinely drives fade rate. Backed by research on dye uptake, and it is the reason condition matters more than cleanser choice.

• The first wash costs the most colour. Supported by work on how dye desorbs, though the popular explanation about colour needing to settle is not quite what the data show.

• Chlorine is a real risk for coloured hair. Clinical guidance supports rinsing before and after swimming.

• The sulphate claim has never been validated. No published studies show sulphates fade colour faster, and lab testing has found sulphate formulas holding colour as well.

• Cool water is sensible but unproven. Universally recommended by salons, with no controlled evidence behind it. Free to do, so do it, but do not build a routine around it.

• Colour safe is a marketing term. More meaningful in principle than sulphate free, with no regulatory definition to back it up.

What To Do Next

Protect it from the sun, stretch the gap between washes, look after the condition of your hair. Then pick a shampoo that suits you rather than one that suits a rule.

For colour maintenance between appointments, especially if you are blonde and watching tone shift, our colour maintenance range is built for exactly that job, and our colour care guidance covers the routine around it.

If your colour looks flat rather than faded, that is usually condition rather than pigment loss. A gloss treatment refreshes tone and shine between salon visits, and a treatment addresses the porosity underneath, which is the one shelf item with real evidence behind it for colour longevity.

And if milder cleansing genuinely suits your hair and scalp, our sulphate free range is there. Choose it because it works for you, not because of the colour rule. If you want to know what is actually in a formula rather than what has been left out, we set out our ingredients and why they are there. Not sure where to start, the hair quiz takes a couple of minutes.

The Short Version

• The sulphate free rule for coloured hair began as marketing and has never been validated by published studies.

• Experts still disagree, which tells you the effect is small either way.

• Sulphate free describes what is missing. Colour safe sounds better but is not a regulated claim.

• Sun exposure is the best evidenced cause of fade. A hat beats a shampoo.

• Porosity and condition drive how fast your colour leaves. Treat the hair, keep the colour.

• The first wash after colour costs the most, so delay it.

• Using both a gentle and a stronger shampoo is a legitimate strategy, not a compromise.

No fuss. Look after the sun, the washes and the condition, and your colour will outlast the argument.