Sodium Lauryl Sulfate
Sodium lauryl sulfate (SLS) is a strong cleansing and foaming surfactant in shampoos, cleansers, and toothpaste. It cleans effectively but is a well-documented skin irritant at higher concentrations, so it is flagged as a caution for sensitive or eczema-prone skin.
SLS is an anionic surfactant that lifts away oil and dirt and creates a rich lather. It is so reliably irritating that dermatology studies use it as a positive control to provoke irritation when testing other substances.
SLS is an irritant, not a true allergen — reactions are dose- and time-dependent, and brief contact in a rinse-off product is usually well tolerated. Even so, people with sensitive skin, eczema, or a compromised skin barrier often prefer milder surfactants.
Who this affects
Caution
- Sensitive skin & eczema: A well-known surfactant irritant that can aggravate a compromised skin barrier.
Frequently asked questions
SLS is an effective cleansing surfactant, but it can strip natural oils and cause dryness or irritant contact dermatitis, especially with prolonged contact or on already-sensitive skin. It is not dangerous for most people in typical rinse-off products, though those prone to irritation may prefer milder formulas. Dermatology guidance notes SLS is more irritating than the related sodium laureth sulfate (SLES).
No. The SLS-causes-cancer claim originated from a late-1990s email hoax and is not supported by evidence; SLS is not classified as a carcinogen by major authorities. The American Cancer Society notes there is little evidence that normal use of cosmetics increases cancer risk. SLS’s genuine drawback is skin and eye irritation, not cancer.
SLS is a classic irritant, not a common true (allergic) sensitiser. It is so reliably irritating that dermatologists use it as the standard reference irritant control during patch testing to help distinguish irritant from allergic reactions. This means most SLS reactions are dose-related irritation rather than an allergy.
If your skin barrier is already compromised, as in eczema, SLS is more likely to provoke dryness and irritant contact dermatitis, so a gentler surfactant is often more comfortable. Choosing milder alternatives (syndets, or products where amphoteric surfactants like cocamidopropyl betaine soften the harshness) can reduce irritation. This is general guidance, not medical advice, and a dermatologist’s assessment is authoritative for your own skin.
Both are anionic cleansing surfactants, but SLES is ethoxylated, which makes it milder and less irritating than SLS. Dermatology sources note SLS may be more irritating than sodium laureth sulfate, which is why sensitive-skin formulas often favour SLES or non-sulfate surfactants. Neither is an allergen concern in the way SLS’s irritancy is.