SLES (sodium laureth sulphate) and SLS (sodium lauryl sulphate) are both anionic surfactants used as the main foaming and cleaning agents in shampoos, body washes and detergents — but SLES is ethoxylated, which makes it milder to skin, more water-soluble, and better at producing a rich, stable foam, while SLS is a harsher, stronger-foaming degreaser.
The two names look almost identical and are constantly mixed up. This guide explains exactly how SLES vs SLS differ, why SLES is usually preferred in skin-contact products, and when each one is the right choice.
SLES vs SLS: quick comparison table
| Property | SLES (Sodium Laureth Sulphate) | SLS (Sodium Lauryl Sulphate) |
|---|---|---|
| Full name | Sodium Lauryl Ether Sulphate | Sodium Lauryl Sulphate |
| Ethoxylated? | Yes (has added ethylene oxide groups) | No |
| CAS number | 68585-34-2 | 151-21-3 |
| Mildness to skin | Milder | Harsher, more irritating |
| Foam | Rich, creamy, stable | Abundant, dense, but less creamy |
| Water solubility | Higher | Lower |
| Typical form | 70% active paste/liquid | Needles, powder or paste |
| Best for | Shampoos, body washes, facial cleansers | Toothpaste, powder detergents, degreasers, lab use |
What is the difference between SLES and SLS?
The difference is one word in the name: ether. SLES is ethoxylated — during manufacture, ethylene oxide units are added to the molecule. SLS has none.
That single change has three practical effects:
- Mildness — the ethoxylation makes SLES significantly gentler on skin and eyes than SLS. This is the main reason it dominates modern personal care.
- Solubility — SLES dissolves more easily in water and tolerates hard water better.
- Foam quality — SLES produces a richer, creamier, more stable foam, which is what consumers associate with a “good” shampoo or body wash.
Why is SLES preferred in shampoos and body washes?
Because it cleans and foams strongly while being milder on skin than SLS. SLS is a powerful surfactant, but at the levels needed for good foam it can be drying and irritating on frequent skin contact. SLES gives formulators most of SLS’s cleaning and foaming power with far less irritation — so it has become the default primary surfactant in shampoos, shower gels, facial cleansers and liquid hand soaps.
In practice, both are usually blended with a mild amphoteric co-surfactant like Cocamidopropyl Betaine to further reduce irritation and boost foam.
When is SLS the better choice?
SLS still has important uses where its strong cleaning and foaming are an advantage and skin-mildness matters less:
- Toothpaste — SLS is the classic foaming agent in toothpaste.
- Powder and paste detergents — strong detergency at low cost.
- Degreasers and industrial cleaners — aggressive cleaning power.
- Laboratory use — SLS (as SDS, sodium dodecyl sulphate) is a standard reagent in biochemistry.
Are SLES and SLS safe?
Both are widely used and well-studied surfactants. SLES is milder; SLS is a stronger irritant, which is why skin-contact products either use SLES or balance SLS with milder co-surfactants. In concentrated form both are irritants and should be handled with gloves and eye protection. Both are readily biodegradable.
A note on the common myth: neither SLES nor SLS is a proven carcinogen. The concern people sometimes raise relates to 1,4-dioxane, a trace by-product that can form during the ethoxylation of SLES — reputable manufacturers purify SLES to keep this to very low, controlled levels, and it is not present in SLS at all.
Frequently asked questions
Is SLES better than SLS?
For skin-contact products like shampoo and body wash, yes — SLES is milder, more soluble and foams better. For toothpaste, powder detergents and degreasers, SLS is often the better, cheaper choice.
What does the “ether” in SLES mean?
It means the molecule is ethoxylated — ethylene oxide groups have been added. This is the chemical difference that makes SLES milder and more soluble than SLS.
Is SLES or SLS more irritating?
SLS is more irritating to skin and eyes. SLES is the milder of the two, which is why it is preferred in products that stay in contact with skin.
Can I substitute SLES for SLS?
Often yes in liquid personal-care formulas, but they behave differently in foam, viscosity and solubility, so the formulation usually needs adjusting rather than a straight swap.
Are SLES and SLS natural?
They are derived from fatty alcohols (often coconut or palm-based) through chemical processing, so they are plant-derived but not “natural” in the unprocessed sense. Both are readily biodegradable.
We supply both surfactants: SLES 70% (Sodium Lauryl Ether Sulphate) and SLS 92% Needles (Sodium Lauryl Sulphate), from trial quantities through to bulk, with batch documentation. Browse our full Surfactants & Cleaning range or request a bulk quote.
For further independent reference, see the Wikipedia entries on sodium laureth sulfate and sodium dodecyl sulfate (SLS).