What Are Sulphates?

Sulphates are one of the most talked-about ingredients in haircare, but most people do not actually know what they are, what they do at a chemical level, or how to spot them on a shampoo bottle. This guide is a proper deep dive into sulphates themselves: the different types, how they work, how they affect your hair, and what "sulphate-free" actually means when you see it on a label.

If you are looking for the functional side — what sulphate-free shampoo actually does for your hair and whether you should switch — we have covered that in our what does sulphate-free shampoo actually do guide. This post focuses specifically on the ingredient itself.

What are sulphates, actually?

Sulphates are a type of surfactant, which is the technical name for a cleansing agent. The word surfactant comes from "surface active agent" and describes any chemical that reduces the surface tension of water so it can lift oil, dirt, and debris away from a surface — including the surface of your hair and scalp.

Surfactants are everywhere. They are in washing-up liquid, laundry detergent, body wash, toothpaste, and shampoo. They work because their molecules have two different ends: one end is attracted to water (hydrophilic) and one end is attracted to oil (hydrophobic). When you work a shampoo into wet hair, the oil-loving ends of the surfactant molecules grab onto the oil and grime on your hair, while the water-loving ends stay connected to the water. When you rinse, the whole lot washes away.

Sulphates specifically are a category of anionic surfactants, which means they carry a negative electrical charge. Anionic surfactants are particularly effective at cleaning because that negative charge binds strongly to positively charged dirt and oil particles. This is exactly why sulphates are so good at stripping oil out of hair. It is also exactly why they strip too much oil out of hair for a lot of people.

The main sulphates you will see in shampoo

Not all sulphates are the same. Some are significantly harsher than others, and knowing the difference matters if you are trying to avoid the really aggressive ones.

Sodium Lauryl Sulphate (SLS)

This is the heavyweight. SLS is the most widely used sulphate in cleaning products globally and has been since the 1930s. It produces enormous amounts of foam, cleans aggressively, and is extremely cheap to manufacture, which is why you will still find it in a huge range of supermarket shampoos, toothpastes, and household cleaners. It is also the most irritating to skin and scalp of the commonly used sulphates. If your hair feels squeaky, stripped, or your scalp gets itchy after washing, SLS is usually the culprit.

Sodium Laureth Sulphate (SLES)

SLES is a slightly gentler relative of SLS, produced by a chemical process called ethoxylation which softens some of the harshness. It still lathers well and cleans effectively, but it is less drying than SLS. SLES is the most common sulphate in professional and mid-range shampoos because it gives the cleansing performance people expect with a bit less of the stripping effect. It is not dramatically gentler in reality though, and many of the same concerns that apply to SLS apply to SLES.

Ammonium Lauryl Sulphate (ALS)

ALS is similar to SLS but uses ammonium rather than sodium. It is just as harsh, and often found in shampoos marketed as "clarifying" because of its strong cleansing power. If you see ALS on a label, treat it the same as SLS.

Ammonium Laureth Sulphate (ALES)

ALES is to ALS what SLES is to SLS: a slightly gentler version of the base ingredient. Still a sulphate, still does the same things as the others, just a touch less aggressive.

Coco-sulphate (Sodium Coco Sulphate)

This one causes a lot of confusion, and you need to watch out for it. Sodium Coco Sulphate is derived from coconut oil, which sounds natural and gentle and is often marketed that way. The chemical reality is different. Coco-sulphate is essentially a mix of different sulphate molecules including SLS itself, and its cleansing effect on hair is virtually identical to straight SLS. If you are trying to avoid sulphates because of hair or scalp concerns, coco-sulphate is not a meaningful alternative. A product containing Sodium Coco Sulphate cannot legitimately be called sulphate-free.

How sulphates actually damage hair

When people say sulphates "damage" hair, they do not mean the hair is being chemically altered in a destructive way. The damage is mechanical and cumulative, and it happens because of how sulphates interact with the structure of the hair itself.

Each hair strand is covered in a protective outer layer called the cuticle, which is made up of tiny overlapping scales that lie flat like roof tiles when the hair is healthy. Underneath the cuticle is the cortex, which contains the pigment that gives your hair its colour and most of its structural protein. A healthy cuticle keeps moisture, colour, and protein locked inside the hair shaft where they belong.

Sulphates, being highly charged anionic surfactants, disturb this structure in two ways. They strip away the natural fatty acid layer that coats and seals the cuticle, which leaves the cuticle scales rough and more prone to lifting. They also penetrate slightly into the cuticle itself, loosening the bonds that hold the scales flat.

When the cuticle is lifted or roughened, three things happen. Moisture escapes from the cortex, leaving hair feeling dry and brittle. Colour pigment washes out with every rinse, which is why coloured hair fades so noticeably with sulphate shampoos. And the rough cuticle surface catches on itself, creating friction that leads to tangling, frizz, and breakage.

This is why sulphate damage is cumulative rather than immediate. One wash will not ruin your hair. But over weeks and months of repeated stripping, the effects build up, and you notice your hair looking duller, feeling drier, and needing more products to manage.

Are sulphates bad for your health?

This is where we need to be honest rather than sensationalist. Sulphates, specifically SLS and SLES, have been the subject of a lot of internet scaremongering over the years, and a fair bit of it is genuinely overblown.

The serious safety bodies that actually test these things — including the Cosmetic Ingredient Review in the US and the Scientific Committee on Consumer Safety in the EU — have consistently concluded that sulphates are safe for use in rinse-off products at standard concentrations. They are not carcinogenic, they are not absorbed into the body in any meaningful way from shampoo, and they do not cause any of the more dramatic health claims that occasionally circulate online.

What they can do is irritate skin and scalp, especially in people with sensitive skin, eczema, or rosacea. The American Academy of Dermatology specifically recommends avoiding sulphate-based cleansers if you have any of these conditions because the irritation is real and well documented.

There is also a specific concern worth knowing about with SLES. The ethoxylation process used to make SLES can leave trace amounts of a contaminant called 1,4-dioxane, which is more concerning than SLES itself. Reputable professional brands purify their SLES to remove this, but it is another reason the gentler alternatives in sulphate-free shampoos are increasingly preferred.

The bottom line: sulphates are not poisonous and will not harm your general health. They can genuinely be rough on your hair and scalp, especially over time, and for people with skin conditions or sensitivities the case for avoiding them is strongest.

The environmental question

The environmental case against sulphates is more mixed than some marketing would have you believe. SLS and SLES are generally considered biodegradable and break down reasonably well in wastewater treatment. They are not considered among the most environmentally damaging ingredients in cosmetics.

However, their production process (particularly for SLES) requires palm oil or petroleum derivatives, both of which carry their own environmental footprints. And while they break down, large volumes of surfactants entering waterways can still temporarily affect aquatic ecosystems. Brands that use plant-derived, readily biodegradable alternative surfactants in sulphate-free formulas generally have a smaller environmental impact overall, though the difference is not as dramatic as some claims suggest.

How to spot sulphates on an ingredients label

Reading a shampoo label can be intimidating because the ingredients list is long and full of chemical names. The good news is sulphates are easy to spot once you know what to look for. Here is the list of names that indicate a sulphate:

• Sodium Lauryl Sulphate (or Sulfate) — SLS
• Sodium Laureth Sulphate (or Sulfate) — SLES
• Ammonium Lauryl Sulphate — ALS
• Ammonium Laureth Sulphate — ALES
• Sodium Coco Sulphate
• TEA Lauryl Sulphate
• TEA Laureth Sulphate
• Sodium Myreth Sulphate

If any of these appear in the ingredients list, the product contains sulphates. The position in the list matters too: ingredients are listed in order of concentration, and surfactants are usually near the top because they make up a significant percentage of the formula. If you see "Sodium Lauryl Sulphate" as the second or third ingredient, it is a major part of the product.

Note that British and American spellings are both valid. "Sulphate" is British, "sulfate" is American. They are identical ingredients, just different spellings.

What "sulphate-free" actually means on a label

There is no single legal definition of sulphate-free in the UK, EU, or US. It is a marketing claim rather than a regulated term, which means the level of rigour behind it varies between brands.

For professional haircare brands, sulphate-free almost always means what you would expect: no SLS, SLES, ALS, ALES, or other sulphate compounds in the formula. Brands like Maria Nila, amika, Olaplex, and milk_shake take this seriously because their target customer is actively looking for these formulations, and misleading on the label would cost them their professional reputation.

For cheaper high street brands, the claim can be looser. A product might be labelled sulphate-free because it has removed SLS, but still contain coco-sulphate or another sulphate-adjacent ingredient. If the claim matters to you, always check the ingredients list rather than relying on the front-of-pack claim alone.

What replaces sulphates in sulphate-free shampoo?

Sulphate-free shampoos still need surfactants to clean. The difference is they use gentler alternatives, typically several of them in combination rather than one dominant ingredient. The most common replacements you will see on sulphate-free labels are:

Cocamidopropyl Betaine. Derived from coconut, this is an amphoteric surfactant (carrying both positive and negative charges) which cleanses gently without stripping. It is one of the most widely used sulphate alternatives.

Sodium Cocoyl Isethionate. A mild anionic surfactant that lathers reasonably well and cleanses effectively without the harshness of SLS.

Decyl Glucoside. A non-ionic, plant-derived surfactant that is particularly gentle and often found in shampoos marketed for sensitive scalps or baby products.

Sodium Lauroyl Methyl Isethionate. A newer-generation mild surfactant that gives a richer lather than many sulphate alternatives while still being gentle.

Coco Glucoside. Another plant-derived glucoside similar to decyl glucoside, widely used in natural and organic-certified shampoos.

These gentler surfactants do not produce the rich, luxurious foam that SLS does. This is the main adjustment people notice when they first switch, and it often leads to the incorrect assumption that sulphate-free shampoos do not clean as well. They clean just as thoroughly, they just do it without the theatrical foam.

So should you avoid sulphates?

The honest answer depends on your hair and scalp.

If you have colour-treated hair, dry or damaged hair, curly or wavy hair, fine or thinning hair, or a sensitive scalp, avoiding sulphates is almost always worth doing. The effects build up slowly but meaningfully, and a switch to sulphate-free is one of the simplest, highest-impact changes you can make to your hair.

If you have robust, healthy, uncoloured hair and a scalp that has never given you any trouble, a standard sulphate-containing shampoo will not wreck your hair. Many people use sulphate shampoos their whole life without any noticeable issues.

The middle ground is using sulphate shampoos occasionally as a clarifying wash (maybe once a month if needed to remove product buildup) and using sulphate-free shampoo for everyday use. This is the approach we often recommend to clients in the salon who do not fit cleanly into either camp.

If you want our recommendations for specific products, our best sulphate-free shampoo for colour-treated hair guide covers our salon-tested picks across brands including Moroccanoil, Joico, Olaplex, milk_shake, Maria Nila, and amika. You can also browse our full sulphate-free shampoo and sulphate-free conditioner collections.

Frequently asked questions

What are sulphates in shampoo?

Sulphates are a type of cleansing agent, specifically anionic surfactants, that remove oil, dirt, and product buildup from the hair and scalp. The most common are Sodium Lauryl Sulphate (SLS) and Sodium Laureth Sulphate (SLES). They are effective at cleaning but can strip natural oils and moisture from hair and scalp, which is why many professional shampoos have moved to gentler alternatives.

What is the difference between SLS and SLES?

SLS (Sodium Lauryl Sulphate) is the harsher of the two and the most common sulphate in cheap supermarket shampoos and toothpastes. SLES (Sodium Laureth Sulphate) is chemically modified through a process called ethoxylation that makes it slightly gentler while still cleaning effectively. SLES is common in professional and mid-range shampoos. Both strip natural oils, but SLS strips more aggressively.

Is coco-sulphate the same as SLS?

Effectively, yes. Sodium Coco Sulphate is derived from coconut oil and often marketed as a natural alternative, but chemically it is very similar to SLS and has essentially the same drying and stripping effect on hair. If you are avoiding sulphates for hair or scalp reasons, coco-sulphate should be avoided too, regardless of how natural it sounds.

Are sulphates safe?

Sulphates are considered safe for use in rinse-off cosmetic products at standard concentrations by regulatory bodies including the Cosmetic Ingredient Review and the EU Scientific Committee on Consumer Safety. They are not carcinogenic and do not cause the more dramatic health issues that sometimes circulate online. However, they can genuinely irritate sensitive skin and scalps, and people with eczema, rosacea, or contact dermatitis are specifically advised to avoid them.

Do sulphates cause hair loss?

Sulphates do not directly cause hair loss. However, persistent scalp irritation from harsh surfactants is not ideal for scalp health, and anyone actively managing thinning hair benefits from a gentler shampoo. Sulphate-free shampoos create a less inflammatory environment on the scalp, which supports healthy hair growth conditions.

Why do sulphates make shampoo foamy?

Sulphates produce abundant foam because of their chemical structure: the highly charged anionic molecules create stable air bubbles when agitated with water. Foam feels satisfying and signals cleaning to most people, but it is a cosmetic effect. Sulphate-free shampoos clean just as effectively with less foam.

What is the difference between sulphate-free and SLS-free?

SLS-free means only that Sodium Lauryl Sulphate has been removed. A product can be SLS-free but still contain SLES, ALS, or coco-sulphate. Sulphate-free is a broader claim meaning no sulphate compounds are present at all. If you are trying to avoid sulphates entirely, sulphate-free is the label to look for, though always check the ingredients list since the term is not strictly regulated.

Is sulfate the same as sulphate?

Yes. Sulphate is the British spelling and sulfate is the American spelling. The ingredients, chemistry, and effects are identical. Both spellings appear on products sold in the UK depending on the manufacturer's country of origin.

Learn more

If you want to understand how switching to sulphate-free shampoo actually changes your hair, read our guide on what does sulphate-free shampoo actually do. For product recommendations specifically for colour-treated hair, our best sulphate-free shampoo for colour-treated hair guide covers our salon-tested picks.

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