SLS and SLES are both cleansing ingredients, but they are not the same.
When comparing Sodium Lauryl Sulfate vs Sodium Laureth Sulfate, the important distinctions are their chemical structures and relative irritation potential.
Comparative testing found SLES produced a far milder skin response than SLS under the conditions studied.[1] This does not make SLS universally “bad” or SLES suitable for everyone. Concentration, contact time and the complete formulation still matter.
In this guide, we’ll cover:
- SLS vs SLES at a glance
- What are SLS and SLES?
- Are SLS and SLES the same?
- What is the chemical difference between SLS and SLES?
- Is SLES gentler than SLS?
- Irritation and allergy: what is the difference?
- Why the finished shampoo matters
- What does SLS vs SLES mean for a sensitive scalp?
- When to seek professional advice
- Why Olsson Scandinavia® uses SLES rather than SLS
- Frequently asked questions
SLS vs SLES at a glance
| Comparison | SLS | SLES |
|---|---|---|
| Full name | Sodium Lauryl Sulfate | Sodium Laureth Sulfate |
| Also written as | Sodium Lauryl Sulphate; Sodium Dodecyl Sulfate (SDS) | Sodium Laureth Sulphate; Sodium Lauryl Ether Sulfate |
| What is it? | Anionic surfactant | Anionic surfactant |
| Main role in shampoo | Cleansing, emulsifying oils and supporting lather | Cleansing, emulsifying oils and supporting lather |
| Are they the same ingredient? | No | No |
| Relative irritation potential | Generally higher | Generally lower than SLS |
| A skin allergen? | Primarily used and discussed as a model skin irritant rather than as a contact allergen | The Cosmetic Ingredient Review reported that SLES was not a skin sensitiser in the available studies.[2] |
| Suitable for everyone? | No ingredient or finished product is universally tolerated | No ingredient or finished product is universally tolerated |
The table gives the short answer. The sections below explain why the distinction matters and why the finished shampoo is more informative than either acronym alone.
What are SLS and SLES?
SLS and SLES are surfactants: ingredients that help water mix with oil and dirt so these substances can be lifted from the hair and scalp and rinsed away.
Both are anionic surfactants, meaning that their water-loving portion carries a negative charge when dissolved. This makes them effective cleansers and useful foaming agents, which is why they appear in shampoos and other rinse-off products.
Lather is not the same as cleansing, but it helps shampoo spread through the hair. A successful formula must balance the removal of sebum and product residue with comfortable use and good cosmetic performance.
What does SLS mean?
SLS stands for Sodium Lauryl Sulfate, or Sodium Lauryl Sulphate in British English. It may also be called Sodium Dodecyl Sulfate or SDS in scientific literature.
SLS cleans effectively, but researchers also use it as a model skin irritant because it can produce a predictable response under controlled conditions. This does not mean every product containing SLS will cause irritation.
What does SLES mean in shampoo?
SLES stands for Sodium Laureth Sulfate, or Sodium Laureth Sulphate. It is sometimes called Sodium Lauryl Ether Sulfate.
In shampoo, SLES helps remove oil, dirt and styling residue while supporting lather. Comparative evidence indicates that its irritation potential is generally lower than that of SLS, although it can still irritate at sufficient concentrations or with prolonged exposure.[1]
For a detailed explanation of SLES, its cleansing performance and how it is used in the Olsson Scandinavia® formula, read our guide to Sodium Laureth Sulphate in shampoo.
Are SLS and SLES the same?
No. They belong to the same broad family of anionic surfactants and perform similar functions, but they are chemically distinct. It is therefore inaccurate to group them together and make a single statement about how “harsh” they are. Each should be considered on its own evidence and within the finished formula.
What is the chemical difference between SLS and SLES?
The structural difference is the ethoxy groups present in SLES. These groups are introduced during manufacture through ethoxylation before the material is sulphated and neutralised.
These additional ethoxy units distinguish SLES structurally from SLS and change some of its physical and chemical characteristics.
It is sometimes said that “SLES is SLS made gentler”. That is an appealing shortcut, but it is not a sufficiently accurate description of the manufacturing chemistry. They are related surfactants with similar jobs, not the same ingredient before and after a simple conversion.
Is SLES gentler than SLS?
SLES generally has lower irritation potential than SLS, although concentration, exposure and formulation still matter. In a controlled patch-testing study, researchers compared SLS and SLES at concentrations from 0.125% to 2%, with exposure periods of 6, 12 and 24 hours. Measurements including transepidermal water loss showed a pronounced reaction to SLS and a far milder reaction to SLES.[1]
This is useful comparative evidence, but it needs context. A closed patch applied for up to 24 hours does not reproduce the way a rinse-off shampoo is normally used. The experiment helps compare the inherent irritation profiles of the surfactants under controlled conditions; it does not predict every person’s response to every finished product.
Two principles are particularly relevant:
- Concentration matters: A stronger exposure can cause a greater response.
- Contact time matters: Leaving a surfactant on the skin is different from briefly applying and rinsing a shampoo.
Irritation and allergy: what is the difference?
The words irritation, sensitivity and allergy are often used as if they mean the same thing. Clinically, they do not.
| Comparison | Irritant contact dermatitis | Allergic contact dermatitis |
|---|---|---|
| Underlying process | Direct damage or disruption to the skin barrier | A delayed immune reaction to a substance after sensitisation |
| Who can experience it? | Anyone, if exposure is sufficiently strong or prolonged; impaired skin may react more readily | Only someone who has become allergic to that particular substance |
| Does prior sensitisation have to occur? | No | Yes |
| Typical influences | Concentration, frequency, duration, friction, rinsing and the condition of the skin barrier | The allergen, degree of exposure and the person’s immune sensitisation |
| How is it investigated clinically? | History and examination; controlled irritancy testing may be used in research | Diagnostic patch testing by an appropriately qualified clinician |
SLS is commonly used in research as a model skin irritant. It is not generally treated as a conventional contact allergen. Similarly, the lower irritation potential of SLES does not make an individual reaction impossible.
The Cosmetic Ingredient Review’s amended safety assessment described SLES as capable of causing dermal and eye irritation, but not as a skin sensitiser in the available evidence. Its conclusion was that SLES ingredients are safe in cosmetic products when formulated to be non-irritating.[2]
What does “formulated to be non-irritating” mean?
“Formulated to be non-irritating” does not mean concentrated SLES is incapable of causing irritation. It means formulators must control its concentration and use it within a finished product designed not to produce unacceptable irritation under normal and reasonably foreseeable conditions of use. Individual reactions can still occur.[2]
Why the finished shampoo matters
Ingredient lists are valuable, but they cannot tell you the concentration of every ingredient or fully predict how those ingredients interact.
| Formulation factor | Why it can influence tolerability |
|---|---|
| Surfactant concentration | Irritation is dose-dependent; the amount used matters |
| Surfactant blend | Surfactants can behave differently in mixtures than they do alone |
| Contact time | A rinse-off shampoo is normally in contact with the scalp briefly, rather than for hours under an occlusive patch |
| Rinsing | Thorough rinsing reduces residue and continuing exposure |
| pH | The finished product’s pH contributes to its overall compatibility with the scalp and hair |
| Frequency of use | Repeated exposure may matter to an already compromised skin barrier |
| Individual skin condition | Active eczema, broken skin or a known contact allergy can change how a person responds |
Research using other mixed surfactant systems shows that the irritation potential of a mixture cannot always be predicted by adding together the profiles of its individual surfactants.[3] This study did not test the Olsson Scandinavia® formula or its particular blend, and it does not prove that every surfactant blend is mild. It supports the principle that finished formulations should be assessed as a whole.
“Sulphate-free” does not automatically mean non-irritating. Such a shampoo still requires cleansing agents, and any surfactant system may be unsuitable for a particular person. The useful question is not simply whether a shampoo contains a sulphate, but which surfactants it uses and how the finished formula performs.
What does SLS vs SLES mean for a sensitive scalp?
If your scalp is sensitive or eczema-prone, choosing shampoo without SLS may be reasonable because SLS has a comparatively higher irritation potential. Avoiding one ingredient cannot, however, guarantee that a finished product will suit you.
Consider the complete formula, whether it contains ingredients you already know you react to, how frequently you wash and whether your scalp is currently inflamed or broken. Apply shampoo primarily to the scalp, use only what you need and rinse thoroughly.
When to seek professional advice
If you have persistent itching, pain, weeping, crusting, hair loss or a worsening rash, seek advice from a pharmacist, GP or dermatologist. Suspected allergic contact dermatitis may require formal diagnostic patch testing; this is different from trying a small amount of a cosmetic at home.
Why Olsson Scandinavia® uses SLES rather than SLS
Olsson Scandinavia® shampoo formulations do not contain SLS. We use SLES because it provides effective cleansing and reliable lather while offering lower irritation potential than SLS.
SLES is not the sole surfactant. It forms part of a blended cleansing system with:
- Sodium Cocoamphoacetate
- Disodium Laureth Sulfosuccinate
- Zinc Coceth Sulfate
This complementary blend was selected to provide effective cleansing and lather. Its ingredient list alone cannot establish tolerability, so the finished formula must be considered. The shampoo is fragrance-free and colourant-free, with a pH range of 5.0 to 5.5.
The finished shampoo has undergone a cosmetic safety assessment, holds Allergy UK’s Allergy Friendly Product Award[4] and is certified by Asthma Allergy Nordic. These credentials relate to the finished product, not SLES as an isolated raw material, and do not guarantee universal tolerance.
Olsson Scandinavia® offers a small product sample so customers can carry out a personal compatibility check before purchasing full bottles of the products. This is not the same as diagnostic patch testing for allergic contact dermatitis and cannot rule out a future reaction. Follow the supplied directions and stop if irritation occurs. If your scalp is actively inflamed, broken or weeping, seek advice from an appropriate healthcare professional before introducing a new product.
Frequently asked questions about SLS and SLES
Are SLS and SLES the same?
No. They are distinct anionic surfactants. Both cleanse and support lather, but SLES contains ethoxy groups that SLS does not and has a different irritation profile.
What is the difference between SLS and SLES?
Their chemical structures differ. Both cleanse effectively, but SLES generally has lower irritation potential than SLS. Concentration, exposure and formulation remain important.
Is SLES gentler than SLS?
Generally, yes. Comparative testing found a pronounced reaction to SLS and a far milder response to SLES under the conditions studied.[1] SLES can still irritate, and individual tolerance varies.
Is SLES better than SLS?
That depends on the intended formula. For shampoo developed with sensitive or eczema-prone scalps in mind, the lower relative irritation potential of SLES may make it a more appropriate choice. The finished product must still be assessed as a whole.
Does SLES mean a shampoo is harsh?
No. SLES on an ingredient list does not establish whether a shampoo will be harsh. Its concentration, surfactant blend, pH, contact time and finished formulation all matter.
Are SLS or SLES skin allergens?
They are primarily discussed here in relation to irritation, not as conventional contact allergens. SLS is a model irritant in research, while the Cosmetic Ingredient Review reported that SLES was not a skin sensitiser in the studies considered.[2] Suspected allergic reactions should be medically assessed.
Does Olsson Scandinavia® shampoo contain SLS or SLES?
Olsson Scandinavia® uses SLES as part of a blended shampoo cleansing system and does not use SLS. Within the range, SLES is used in shampoo products only.
SLS and SLES cleanse in similar ways, but they are not the same ingredient.
SLES generally has lower irritation potential than SLS, while the complete shampoo determines how the ingredients are presented to the scalp.
This is why Olsson Scandinavia® uses SLES within a blended, fragrance-free and colourant-free shampoo formula created with sensitive scalps in mind.
This article provides general information and is not medical advice. If you have persistent scalp symptoms, suspected contact allergy or a diagnosed skin condition, seek individual advice from an appropriate healthcare professional.
Further reading and references
- Löffler H, Happle R. Profile of irritant patch testing with detergents: sodium lauryl sulfate, sodium laureth sulfate and alkyl polyglucoside. Contact Dermatitis. 2003;48(1).
- Cosmetic Ingredient Review Expert Panel. Final report of the amended safety assessment of sodium laureth sulfate and related salts of sulfated ethoxylated alcohols. International Journal of Toxicology. 2010;29(4 Suppl).
- Hall-Manning TJ, Holland GH, Rennie G, Revell P, Hines J, Barratt MD, Basketter DA. Skin irritation potential of mixed surfactant systems. Food and Chemical Toxicology. 1998;36(3).
- Allergy UK. Olsson Haircare and Shampoo: Allergy Friendly Product Award.
