Sodium lauryl sulfate (SLS) is in a surprisingly wide range of everyday products, from your shampoo and toothpaste to engine degreasers and even some foods. It’s a surfactant, meaning it helps oil and water mix together so dirt and grease can be washed away. That same property makes it useful as a foaming agent, emulsifier, and cleaner across dozens of product categories.
Personal Care Products
This is where most people encounter SLS. It’s the ingredient responsible for the lather you get when you wash your hands, shampoo your hair, or brush your teeth. You’ll find it in shampoo, body wash, hand soap, facial cleansers, bubble bath, shaving foam, and toothpaste. In all of these, SLS serves two roles: it bonds oil and water molecules together so they can lift away dirt and oils from your skin or hair, and it creates the foamy texture people associate with a thorough clean.
Personal care products generally use SLS in lower concentrations than industrial cleaners. The Cosmetic Ingredient Review panel has recommended that products applied to the skin contain no more than 1% SLS, partly because the compound can deposit on hair follicles and potentially cause irritation at higher levels. Rinse-off products like shampoo and body wash pose less risk than leave-on products because the contact time with your skin is brief.
Household Cleaning Products
SLS works the same way in cleaning products as it does on your body: it wets surfaces, breaks up oils, and suspends dirt so it rinses away cleanly. You’ll find it in dish soap, laundry detergent, and general-purpose surface cleaners. The concentrations in household cleaners are moderate, higher than in personal care items but lower than in industrial formulas.
Industrial and Commercial Products
At the heavy-duty end of the spectrum, SLS shows up in engine degreasers, floor cleaners, and car wash products. These formulations use significantly higher concentrations to tackle grease and grime that household products can’t handle. The American Cleaning Institute notes that workplace protections are typically implemented around these products to avoid unsafe skin exposure at those concentrations.
Food Products
This one catches most people off guard. The FDA permits SLS as a food additive in specific, tightly controlled amounts. It’s approved as an emulsifier in egg whites (up to 1,000 parts per million in egg white solids and 125 parts per million in frozen or liquid egg whites), as a whipping agent in marshmallows (up to 0.5% by weight of the gelatin used), and as a surfactant in certain fumaric acid-acidulated fruit juice drinks and dry beverage bases at no more than 25 parts per million in the finished drink. It also serves as a wetting agent during the processing of crude vegetable oils and animal fats, at levels not exceeding 10 parts per million. These are trace amounts, far below what you’d encounter in a bottle of shampoo.
How to Spot It on a Label
SLS doesn’t always go by its most common name. On ingredient lists you might see it called sodium dodecyl sulfate, sodium lauryl sulphate (the British spelling), dodecyl sodium sulfate, or sodium n-dodecyl sulfate. These are all the same compound. Don’t confuse it with sodium laureth sulfate (SLES), which is a related but chemically distinct surfactant that’s generally considered milder on skin.
SLS and Skin Irritation
SLS is an irritant, not an allergen. The distinction matters. It doesn’t trigger an immune response the way a true allergen would. Instead, it strips natural oils from your skin, and at high enough concentrations or long enough contact times, that causes redness and irritation. In patch testing on volunteers, concentrations as low as 0.25% applied under occlusion for 24 hours produced borderline irritant reactions, with the strongest responses appearing at 48 hours rather than immediately. This delayed reaction means you might not connect your irritation to the product causing it.
For most people using normal consumer products, the concentration and brief contact time don’t cause problems. But if you have eczema, rosacea, or generally sensitive skin, you may notice dryness or irritation from SLS-containing body washes or facial cleansers. Switching to an SLS-free formula often resolves the issue.
SLS and Canker Sores
If you’re prone to canker sores (aphthous ulcers), the SLS in your toothpaste may be making them worse. SLS can irritate the soft tissue inside your mouth, and for people already susceptible to canker sores from factors like stress, poor sleep, or acidic foods, this added irritation can increase the frequency of outbreaks. SLS-free toothpastes are widely available, and many people who make the switch report fewer canker sores. The toothpaste still cleans effectively without SLS; you just won’t get as much foam.
Is SLS Dangerous?
A persistent internet claim links SLS to cancer. There’s no credible evidence supporting this. A comprehensive review published in Environmental Health Insights examined both human and environmental toxicity data and concluded that SLS is safe for use in household cleaning products at typical concentrations. Regulatory bodies including the FDA and the Cosmetic Ingredient Review panel permit its use in food, personal care products, and cleaning products within established concentration limits.
The real concern with SLS is straightforward irritation, not toxicity. At high concentrations or with prolonged skin contact, it dries and irritates. At the levels found in consumer products, and with the short contact times of normal use, most people tolerate it without any issues. If you do experience dryness, irritation, or recurring canker sores, SLS-free alternatives exist in nearly every product category.