CAS Number: 151-21-3
Other names: Sodium dodecyl sulfate (SDS), Sodium laurilsulfate, Lauryl sodium salt
What is Sodium Lauryl Sulfate?
Sodium Lauryl Sulfate (SLS) is an anionic surfactant derived from coconut or palm kernel oil (or synthetically). It is one of the most widely used foaming and cleansing agents in personal care and household cleaning products because it is cheap, effective, and produces rich lather.
Chemical Properties
| Property | Value |
|---|---|
| Chemical formula | C12H25NaO4S |
| Molecular weight | 288.38 g/mol |
| Appearance | White or cream-colored powder, crystals, or clear liquid (in solutions) |
| Solubility in water | ≈ 150 g/L (20 °C) |
| pH (1% solution) | 7.5–9.5 |
| Critical micelle concentration (CMC) | ≈ 8.2 mM at 25 °C |
How is SLS Produced?
- Lauryl alcohol (dodecanol) is obtained from coconut or palm kernel oil via hydrogenation using the catalyst copper-chromium oxide.
- Lauryl alcohol is sulfated with sulfur trioxide (SO₃) or chlorosulfonic acid → lauryl hydrogen sulfate.
- Neutralization with sodium hydroxide (NaOH) → Sodium Lauryl Sulfate + water.
Common Uses
- Toothpastes (foaming & cleaning)
- Shampoos, body washes, facial cleansers
- Bubble baths and bath bombs
- Household cleaners, dish soap, laundry detergents
- Engine degreasers and car wash soaps
- Industrial emulsifier and wetting agent
- Laboratory reagent (protein denaturation in SDS-PAGE)
Is Sodium Lauryl Sulfate Safe?
Skin & Eye Irritation
SLS is a known irritant at higher concentrations (>2–5%). It can cause:
- Skin dryness and barrier damage
- Contact dermatitis in sensitive individuals
- Eye irritation (reason many “no-tears” baby shampoos avoid it)
The Cosmetic Ingredient Review (CIR) Expert Panel concluded SLS is safe in formulations designed for discontinuous, brief use followed by thorough rinsing (e.g., shampoos, cleansers). Leave-on products should contain ≤1%.
Cancer & Toxicity Myths
No credible evidence shows SLS causes cancer. The “SLS causes cancer” rumor originated from chain emails in the 1990s and has been repeatedly debunked by:
- American Cancer Society
- Cancer Research UK
- Cosmetic Ingredient Review
- EU Scientific Committee on Consumer Safety
Oral Toxicity
LD50 (rat, oral): 1,288 mg/kg — relatively low acute toxicity (comparable to table salt).
Environmental Impact
- Biodegradability: Readily biodegradable (>90% in 28 days)
- Aquatic toxicity: Moderately toxic to aquatic life (EC50 ≈ 1–10 mg/L)
- Modern production mostly uses plant-derived sources, but palm oil sourcing can contribute to deforestation if not RSPO-certified.
SLS vs SLES vs SCS
| Surfactant | Full Name | Irritation Potential | Foam | Common Use |
|---|---|---|---|---|
| SLS | Sodium Lauryl Sulfate | High | Excellent | Toothpaste, strong cleansers |
| SLES | Sodium Laureth Sulfate | Moderate | Excellent, creamier | Most shampoos & body washes |
| SCS | Sodium Coco-Sulfate | Slightly lower than SLS | Good | “Natural” brand cleansers |
How to Identify SLS on Labels
Look for:
- Sodium lauryl sulfate
- Sodium dodecyl sulfate
- Sulfuric acid, monododecyl ester, sodium salt
- SDS or SLS (in lab settings)
Alternatives for Sensitive Skin
- Sodium Cocoyl Isethionate (SCI)
- Coco-Glucoside, Decyl Glucoside, Lauryl Glucoside
- Sodium Lauroyl Sarcosinate
- Disodium Laureth Sulfosuccinate
- Cocamidopropyl Betaine (often combined with milder surfactants)
References & Regulatory Status
- FDA: Generally Recognized as Safe (GRAS) as a multipurpose food additive (limited use)
- EU: No restrictions when used appropriately in rinse-off products
- CIR (2021): Safe as used in present practices of use and concentration
- EWG Skin Deep score: 1–2 (low hazard, depending on usage)
Interactive FAQ
No. This myth originated from a 1990s hoax email. Every major health authority confirms there is no credible evidence that SLS is carcinogenic.
SLS is a strong surfactant that denatures proteins in the skin barrier and extracts lipids, especially at >2% concentration or in leave-on products. Sensitive skin, eczema, and rosacea sufferers are most affected.
Yes. The ethoxylation process makes SLES significantly milder while retaining excellent foaming properties. Most modern shampoos use SLES instead of SLS.
It can trigger or worsen canker sores in susceptible people and may cause temporary taste alteration. Many “SLS-free” toothpastes are available for this reason.
No. The source does not change the chemical structure, irritation potential, or safety profile.
Sodium Coco-Sulfate is a mix of chain lengths (C12–C18), making it slightly milder than pure SLS. Brands use it to advertise “SLS-free” while keeping good foam.
Penetration through intact skin is <1%, and any absorbed amount is rapidly excreted in urine. No significant systemic exposure occurs with normal cosmetic use.
No. It is fully approved in the EU with no concentration restrictions in rinse-off products (≤1% in leave-on).