Sodium Lauryl Sulfate (SLS) for Soap and Cleanser Makers

SLS shows up in more formulas than almost anything else in this category, and it also gets more misinformation thrown at it than almost any other ingredient a maker deals with. Worth separating what is actually true from what is internet folklore, and worth knowing exactly how it needs to appear on your paperwork.

What SLS is and what it does

Sodium Lauryl Sulfate is an anionic surfactant, meaning it carries a negative charge that lets it lift oil and dirt away from skin or hair and let water rinse it off. It is one of the most effective and least expensive surfactants available, which is exactly why it shows up in shampoos, body washes, liquid hand soaps, and some solid syndet bars. Its foam is generous and its cleaning power is strong, sometimes strong enough to be the issue.

INCI and identification

Detail	Value
INCI name	Sodium Lauryl Sulfate
Also called	Sodium dodecyl sulfate
CAS number	151-21-3
Function	Surfactant / cleansing agent
Typical use level	Varies widely by product type; check your supplier's technical data sheet for the specific grade you're using

Note that SLS as a raw material is sometimes sold as a solution (in water, at a stated percentage) rather than pure powder. If your supplier ships you a 30% aqueous solution, the concentration you declare in your formula is the actual SLS content in the finished product, not the percentage of the raw material you weighed in. This is the same "expand the blend" math you'd apply to any diluted raw material or supplier blend: multiply the supplier's stated concentration by how much of that raw material you used, to get the true finished-product percentage.

The irritation question, honestly

SLS has a reputation, some of it earned, some of it exaggerated. It is a strong surfactant and can be more irritating to skin and eyes than gentler surfactants, especially at higher concentrations, on already-compromised skin, or in leave-on contact. This is real and worth respecting in formulation decisions. It is not, however, the industry-wide banned substance that certain corners of the internet describe. It remains a widely used, generally recognized cleansing agent in rinse-off products at appropriate levels.

Practical formulation habits that address the real irritation concern:

• Keep total anionic surfactant concentration reasonable and consider blending SLS with milder co-surfactants
• Favor rinse-off applications over anything meant to sit on skin
• Watch pH of the finished product, since surfactant systems that skew far from skin-neutral pH tend to be more irritating regardless of which surfactant is doing the cleansing
• Consider your target audience; a product marketed for sensitive skin or children may call for a gentler surfactant choice entirely

Declaring SLS in a notification

Because SLS is typically used as a primary rinse-off surfactant, it is usually present at a meaningful percentage of the formula, not a trace amount, so its concentration or concentration range needs to be accurate on whatever notification you file. In Canada's CNF, for example, ingredients are listed by INCI name with concentration or a concentration range, and SLS at, say, 8 to 12% of a body wash needs to appear as such, not folded silently into "surfactant blend."

Where this gets messed up in practice:

1. Trade name confusion. A supplier's brand name for their SLS grade never belongs on the filing. Only the INCI name does.
2. Forgetting the dilution math. If you bought a 28 to 30% SLS solution and used it at 30% of your formula, the actual SLS content is roughly 8.4 to 9%, not 30%. Filing 30% overstates it substantially.
3. Blend confusion. Some commercial surfactant blends include SLS alongside other surfactants, foam boosters, or thickeners. Each component of a blend needs to be identified and its true concentration calculated the same way.

SLS is not a fragrance allergen or a Hotlist entry

To be clear about scope: SLS is a surfactant, not a fragrance ingredient, so it has no relationship to Canada's fragrance allergen disclosure requirements (List 1 mandatory April 12, 2026; List 2 mandatory August 1, 2026). Always check the current Cosmetic Ingredient Hotlist directly for any concentration limits or conditions that may apply to surfactants generally, since restricted-list details can change and a facts sheet like this one is a starting point, not the final word.

The bigger picture

SLS is a well-understood, well-documented ingredient, which actually makes it one of the easier ones to get right on paper. The harder part is usually catching the dilution math when a supplier blend or aqueous solution is involved, since that's where the declared concentration and the real concentration quietly diverge. Cosmetic Comply's ingredient mapping step is built exactly for that, expanding blends into components and carrying the real percentages through to the filing, so an ingredient like SLS ends up declared at what it actually is in your finished product, not at the raw material weight you started with.