Sodium Laureth Sulphate is an effective cleansing ingredient used in shampoos and other rinse-off products. It helps remove oil and everyday build-up, creates a consistent lather and makes shampoo easier to distribute through wet hair.
However, the presence of SLES on an ingredient list does not, by itself, tell you whether a shampoo will be gentle or irritating. Its concentration, the surrounding surfactants, finished pH, contact time and normal conditions of use all matter.
Image note: An illustrative representation of Sodium Laureth Sulphate. The physical form of commercial SLES raw materials can vary.
SLES at a glance
| SLES at a glance | What the evidence tells us |
|---|---|
| What is it? | An anionic surfactant used in shampoos and other rinse-off cleansers |
| Why is it used? | Effective cleansing, foam, distribution and rinseability |
| Can it irritate? | Yes, depending on concentration, exposure and formulation |
| Is it a skin sensitiser? | It was not identified as a sensitiser in the CIR evidence reviewed |
| Is it the same as SLS? | No. They are related but chemically distinct surfactants |
| What matters most? | Concentration, surfactant blend, pH, contact time and the finished-product assessment |
In this guide, we’ll cover:
- What Sodium Laureth Sulphate is
- What SLES does in shampoo
- What “formulated to be non-irritating” means
- The difference between irritation and allergy
- What controlled irritation research found
- Why the complete surfactant system matters
- How SLES is used in Olsson Scandinavia® shampoo
- What the raw-material specification says about 1,4-dioxane
- What sensitive or eczema-prone users should consider
- People also ask
What is Sodium Laureth Sulphate?
Sodium Laureth Sulphate, also written Sodium Laureth Sulfate and commonly shortened to SLES is an anionic surfactant.
Surfactants have one part that interacts with water and another that interacts with oils. This allows them to surround sebum, styling-product residue and oily dirt so that water can carry this material away during rinsing.
SLES belongs to a group of ethoxylated alkyl sulphates. The ethoxylation stage introduces ether-linked units that distinguish it chemically from Sodium Lauryl Sulphate.
Commercial SLES is generally a mixture of closely related compounds rather than one completely uniform molecule.
SLES and SLS have similar names, but they are not interchangeable ingredients. This article concentrates on SLES. For the full comparison, read SLS and SLES: What’s the Difference?
What does SLES do in shampoo?
It cleanses the scalp and hair
Sebum has an important protective role, but excess oil can combine with sweat, dead skin cells, environmental particles and styling-product residue.
SLES helps loosen and disperse this build-up so that it can be carried away when the shampoo is rinsed.
The objective is not to remove every trace of the scalp’s natural oil. It is to remove unwanted accumulation and leave the hair feeling comfortably clean.
It supports effective rinsing
Oil and water do not ordinarily mix. As a surfactant, SLES helps oily material disperse in water so that sebum and other residues can be removed more effectively.
It creates consistent lather
Foam is not the mechanism that cleans the hair, and a low-foaming shampoo is not necessarily less effective.
Lather does, however, help people see and feel where shampoo has been applied. It makes the product easier to distribute through wet hair and contributes to a consistent washing experience.
It supports formula performance
SLES can contribute to the texture, spreadability and overall sensory performance of a liquid shampoo.
A shampoo must be practical and pleasant to use as well as technically effective.
Is Sodium Laureth Sulphate safe?
The Cosmetic Ingredient Review Expert Panel has assessed SLES and related ingredients for use in cosmetics.
Its safety assessment found that Sodium Laureth Sulphate has the potential to irritate the skin and eyes, but it was not identified as a sensitiser in the evidence reviewed.[1]
The panel concluded that these ingredients should be used only when they can be “formulated to be non-irritating”.
That does not mean concentrated SLES is incapable of causing irritation or that every SLES-containing product will suit every individual.
It means SLES must be considered within the finished cosmetic product and under its intended conditions of use.
The CIR assessment noted that although SLES and the related sulphated ethoxylated alcohols it reviewed have irritation potential, they are not regularly found to be irritating in practice because of the formulations in which they are used.[1]
What does “formulated to be non-irritating” mean?
Raw-material safety information may describe a concentrated substance before it has been diluted and combined with the other ingredients in a shampoo.
That is not the same exposure as briefly using a finished rinse-off product.
| Formulation factor | Why it matters |
|---|---|
| SLES concentration | Irritation potential generally increases with concentration and exposure |
| Surfactant blend | SLES interacts with the other cleansing ingredients in the formula |
| Finished pH | Olsson Scandinavia® shampoo is adjusted to pH 5.0–5.5, although pH alone cannot prove tolerability |
| Contact time | Shampoo is briefly applied and rinsed away rather than deliberately left on the skin |
| Finished-product assessment | The complete formula and its foreseeable use are assessed—not only the raw ingredient |
“Formulated to be non-irritating” therefore describes a formulation objective and safety requirement. It is not an absolute promise that no person could ever experience discomfort or a reaction.
Irritation is not the same as allergy
The terms irritation, sensitivity and allergy are often used interchangeably. Clinically, however, they describe different things.
| Reaction | What happens? | Is prior sensitisation required? |
|---|---|---|
| Irritant contact dermatitis | A substance directly disrupts or inflames the skin barrier | No |
| Allergic contact dermatitis | The immune system reacts to a particular substance | Yes |
| General sensitivity | A broad description of unpleasant or poorly tolerated reactions | Not necessarily |
Irritant contact dermatitis
Irritant contact dermatitis does not require a previous allergy. Given a sufficiently strong concentration or long exposure, an irritant reaction can potentially occur in anyone.
People with a weakened skin barrier, including some people with eczema, psoriasis and other skin conditions may respond more readily. Possible symptoms include burning, stinging, dryness, redness, soreness or cracking.
Allergic contact dermatitis
Allergic contact dermatitis is a delayed immune reaction. A person must first become sensitised to a particular substance, after which a relatively small exposure may trigger a reaction.
Diagnostic patch testing carried out by a dermatology service is principally used to investigate this type of delayed contact allergy.
The fact that an ingredient can cause irritation does not automatically make it an allergen. SLES was not identified as a sensitiser in the evidence reviewed by the CIR Expert Panel.[1]
What did the controlled irritation research find?
A controlled study examined SLS and SLES solutions at several concentrations. The solutions were applied to the skin under patches for 6, 12 or 24 hours.
Under these experimental conditions, researchers reported a pronounced skin reaction to SLS and a far milder reaction to SLES. The effects associated with SLS also remained detectable for longer.[2]
The experiment assessed individual detergent solutions rather than finished rinse-off shampoos. It demonstrates a difference between the surfactants under controlled conditions, but does not predict how every shampoo will perform.
Prolonged exposure under a patch is not equivalent to briefly using a formulated shampoo and rinsing it away, which is the intended use for our formula.
Why the complete surfactant system matters
Modern shampoos generally use several surfactants rather than relying on one cleansing ingredient.
Each surfactant can contribute different cleansing, foam, rinsing, texture and sensory characteristics. These ingredients also interact inside the finished formula. Again this is very important.
Note: Research involving mixed surfactant systems has shown that irritation potential cannot always be predicted by simply adding together the irritation potential of each ingredient.
In one human study, certain combinations produced a lower acute irritation response than would have been expected from the individual surfactants.[3]
That study did not assess the combination used in Olsson Scandinavia® shampoo. It supports the broader formulation principle that a surfactant system must be considered as a whole, but does not prove the tolerability of a particular untested blend.
How SLES is used in Olsson Scandinavia® shampoo
| Formula characteristic | Olsson Scandinavia® shampoo |
|---|---|
| Role of SLES | Effective cleansing and dependable foam |
| Accompanying surfactants | Sodium Cocoamphoacetate, Disodium Laureth Sulfosuccinate and Zinc Coceth Sulfate |
| Finished pH | 5.0–5.5 |
| Fragrance | None |
| Colourants | None |
| SLS | Not included |
| Product safety | Finished cosmetic safety assessment completed |
| Independent recognition | Allergy UK Allergy Friendly Product Award and Asthma Allergy Nordic approval. |
SLES is not the entire Olsson Scandinavia® cleansing system. It is combined with three accompanying surfactants so that different ingredients contribute to cleansing, foam, distribution and rinsing.
These formula characteristics do not guarantee that every person will tolerate the shampoo. They demonstrate why the complete finished product is more informative than judging it from one ingredient name.
The independent approvals also apply to the finished shampoo, not to SLES as an isolated ingredient.
Allergy UK currently includes Olsson Scandinavia® Haircare within its “Unlikely to Cause a Reaction” product category.[5] This provides useful reassurance, but does not guarantee individual tolerance.
What about 1,4-dioxane?
1,4-dioxane is not deliberately added to Olsson Scandinavia® shampoo. It can occur as an unintended trace by-product during the manufacture of ethoxylated ingredients, including SLES.
The supplier specification for the concentrated SLES raw material used in Olsson Scandinavia® shampoo sets a 1,4-dioxane specification of 0–14 parts per million, tested using the supplier’s internal analytical method.[4]
Note: This is a raw-material specification not a finished-shampoo test result.
Because SLES forms only one part of the formula, the contribution from this particular raw material would be reduced when incorporated into the shampoo. This does not establish the total amount in the finished product or account for every other raw material.
We do not describe the finished shampoo as “1,4-dioxane-free” unless absence has been demonstrated through appropriate finished-product testing.
Potential trace impurities and raw-material specifications are considered as part of the product information and cosmetic safety assessment.
Is SLES suitable for sensitive or eczema-prone scalps?
No cosmetic product can be guaranteed to suit every person with sensitive skin.
Eczema, Psoriasis and skin sensitivity, varies considerably between individuals. Personal tolerance may also change depending on whether the skin is settled or experiencing an active flare.
Factors that can affect the experience of a shampoo include:
- The condition of the skin barrier
- The concentration and combination of surfactants
- Fragrance exposure
- Product pH
- Water temperature
- Washing frequency
- Contact time
- How thoroughly the shampoo is rinsed away
Skin that is actively inflamed, cracked or weeping may sting in response to products that are otherwise tolerated when the condition is settled.
Can a home compatibility test help?
Trying a small amount of a finished product on a limited area may provide some practical information about how your skin responds to that formula under those particular conditions.
However, a home compatibility test cannot diagnose contact allergy, guarantee future tolerance or replace professionally supervised diagnostic patch testing.
A patch test should follow the supplied instructions.
For effective cleansing without fragrance
Our fragrance-free shampoos for sensitive scalps are designed to provide salon-performance cleansing without fragrance or colourants.
SLES is used as part of a blended surfactant system in a finished formula with a pH of 5.0–5.5.
For those who are particularly cautious about introducing a new product, a small compatibility sample offers an opportunity to experience the formula before purchasing a full-size product.
It cannot establish that continued use will be reaction-free and should not be confused with diagnostic patch testing.
People also ask
What is SLES in shampoo?
SLES is Sodium Laureth Sulphate, an anionic surfactant that helps shampoo remove sebum, dirt and product residue. It also supports lather, distribution and rinsing.
Is Sodium Laureth Sulphate safe?
The CIR Expert Panel concluded that SLES should be used only when it can be formulated to be non-irritating. Its suitability therefore depends on its concentration, the complete formulation and normal conditions of use.
Is SLES a skin allergen?
SLES was not identified as a skin sensitiser in the evidence reviewed by the CIR Expert Panel.
It can cause irritation depending on concentration, exposure and formulation. Irritation and allergic sensitisation are different biological processes.
Does SLES contain 1,4-dioxane?
1,4-dioxane is not deliberately added, but it can occur as an unintended trace by-product during SLES manufacture.
Olsson Scandinavia®’s supplier specification sets a 1,4-dioxane range of 0–14 ppm for the concentrated SLES raw material. This is not a finished-shampoo test result, and we do not claim the shampoo is 1,4-dioxane-free.
Is SLES suitable for an eczema-prone scalp?
Individual tolerance varies. A well-assessed rinse-off formula may be suitable for many sensitive users, but no cosmetic can be guaranteed to suit everyone with eczema.
The condition of the skin barrier, complete formula and way the product is used all matter.
SLES is an effective cleanser and how it is formulated matters.
The complete formula tells us more than one ingredient name.
SLES can irritate under sufficiently strong or prolonged exposure. It was not, however, identified as a skin sensitiser in the evidence reviewed by the Cosmetic Ingredient Review Expert Panel.
In a finished shampoo, concentration, surfactant combination, pH, contact time and rinse-off use all influence how the product performs.
At Olsson Scandinavia®, SLES provides effective cleansing, foam and rinseability as part of a multi-surfactant system. The fragrance-free, colourant-free shampoo has a finished pH of 5.0–5.5 and has undergone its own cosmetic safety assessment.
It has also received the Allergy UK Allergy Friendly Product Award and is approved by Asthma Allergy Nordic.
The complete formulation, and the way it is used, is more informative than seeing “Sodium Laureth Sulphate” on an ingredient list and judging the product by that name alone.
General educational information only. This article does not diagnose or treat a scalp or skin condition. Seek advice from a healthcare professional if you have persistent symptoms, suspected contact allergy or a severe eczema flare.
Further reading and references
- Final report of the amended safety assessment of Sodium Laureth Sulfate and related ingredients
- Profile of irritant patch testing with Sodium Lauryl Sulfate and Sodium Laureth Sulfate
- Skin irritation potential of mixed surfactant systems
- SLES supplier technical specification: 1,4-dioxane specification of 0–14 ppm, tested using the supplier’s internal method. Held within the Olsson Scandinavia® product information documentation.
- Olsson Scandinavia® Haircare and Shampoo - Allergy UK approved-product listing
