Is sodium lauryl sulfate (SLS) safe? Irritation, the cancer claim, and the rules

Cleansing (surfactant) ingredient · Also known as: SLS, Sodium lauryl sulphate · Reviewed Sep 19, 2026 · 14 sources

Where sodium lauryl sulfate (SLS) is allowed

What is sodium lauryl sulfate (SLS)?

SLS is a detergent, the word the CIR uses for it: a cleansing ingredient added to products that are rinsed away. It is spelled sulphate in the UK. It is not the same as sodium laureth sulfate (SLES): the CIR calls them different chemicals, assesses them separately, and concluded SLES is safe as presently used while noting it can irritate the eyes and skin. The CIR was set up by the cosmetics industry in 1976 and describes itself as an independent panel.

Why it's used, and where you'll find it

SLS cleans. The CIR describes it as a detergent for products meant for brief use followed by thorough rinsing, and dentistry reviews describe its use in toothpastes. In the US it also has narrow food-additive uses, such as an emulsifier in egg whites and a whipping agent in marshmallows.

• shampoo
• body wash and liquid soap
• toothpaste
• household cleaning products
• a few foods (US-approved additive uses)

What the research and regulators say

Irritation is the well-established concern

The CIR's 1983 report found SLS and ammonium lauryl sulfate irritating in patch tests at 2 percent and above, with irritation rising with concentration and contact time, sometimes unnoticed. It concluded they appear safe in formulations designed for brief use followed by thorough rinsing, and that products for prolonged skin contact should not exceed 1 percent. Health Canada's page on SLS says the panel looked at it again in 2004, amended the review in 2010, and continues to maintain its position. ^{[6, 11, 14]}

Hair follicles and pores

The same report described animal findings for formulators to weigh: radio-labelled SLS collected on rat skin and in hair follicles, and 1 and 5 percent SLS produced comedones on rabbit ears. It flagged possible hair loss and comedone formation. These are decades-old animal data, and, according to its abstract, a 2007 rabbit-ear study that tested SLS alongside other cosmetic materials did not list it among those it found comedogenic. ^{[6, 10]}

The cancer claim

The CIR report said SLS was not carcinogenic in experimental animals, though it noted severe skin changes in treated mice and said tumour-enhancement tests were needed. A 2015 peer-reviewed review says there is no scientific evidence SLS is a carcinogen, traces the claim to misread studies in which SLS was only a carrier, and reports it is not listed as a carcinogen by IARC, the US National Toxicology Program or California's Proposition 65. All but one of its authors were employed by a household-products company, which they disclose. Separately, IARC's public list of classified agents (Volumes 1 to 142) and the Proposition 65 list of 31 July 2026 have no entry for SLS; absence from IARC's list means it has not been classified, not that it was tested and cleared. ^{[6, 7, 12, 13]}

A by-product sometimes mentioned: 1,4-dioxane

Health Canada's page says small amounts of 1,4-dioxane, a by-product of ethoxylation, may be found in ingredients such as PEGs and SLS, and can be controlled by purification. It says high exposure to dioxane has been linked to kidney and liver damage and, in some laboratory animals, to cancer, but that dioxane exposure from cosmetics was evaluated under Canada's Chemicals Management Plan and found to be safe. ^[11]

Toothpaste and canker sores

A 2019 systematic review of four small crossover trials (124 participants) found SLS-free toothpaste reduced the number, duration, frequency and pain of ulcers in people with recurrent canker sores. Its authors say better-designed trials are still needed. A 2022 scoping review reported mouth-tissue irritation in some studies and described the evidence for SLS-free toothpaste as limited. ^{[8, 9]}

Who might choose to avoid it

People with sensitive or easily irritated skin, or a history of reacting to cleansers, may prefer SLS-free products. The same goes for people with frequent canker sores who want to try an SLS-free toothpaste, though the reviewers call for better trials and one describes the evidence as limited.

How to spot it on a label

Look for 'Sodium Lauryl Sulfate' (or 'Sulphate') on ingredient lists. Sodium Laureth Sulfate and Ammonium Lauryl Sulfate are different ingredients with their own names.

Frequently asked questions

Related ingredients

• Fragrance (Parfum)
• Phenoxyethanol
• Propylene glycol

This page summarizes what regulators and published research say, as of the review date above. Rules and evidence change; check the linked sources for the latest. It is general information, not medical advice — talk to a doctor or pharmacist about your own health.