Does a shampoo additive (sodium lauryl sulfate) cause cancer?

Dear Reader, 

Who knew keeping clean could be so complicated? While some shampoos and hair products may contain ingredients that have been linked to increased risk of cancer, presently, there’s no scientific evidence that sodium lauryl sulfate (SLS) or sodium laureth sulfate (SLES) are among these cancer-causing chemicals. While the mention of “skin irritation” might have you itching to toss out your sulfate-containing shampoos, unless you have skin sensitivities or an SLS allergy, this may not be an issue you encounter. If cancer concerns are occupying your shower thoughts, you might instead steer clear of products containing ingredients such as formaldehyde, formalin, methylene glycol, and benzene.  And if you’re still torn on whether or not to go sulfate-free, read on to find out more about SLS and SLES before changing up your hair care routine. 

As you mentioned, SLS and SLES are often used in shampoos because of their ability to lather and foam, but did you know that their function goes beyond just making bubbles? These sulfates are surfactants—chemicals that can help separate oil and dirt from your hair and skin—that help to keep you clean! This ability to lift dirt and oil is why sulfates are used in a variety of cleaning products from shampoo and toothpaste to carpet and garage cleaners. 

For many, the variety of products containing SLS and SLES is the primary safety concern. It may calm your nerves to know that a number of reputable organizations recognize SLS and SLES as a product safe for various uses. The Cosmetic Ingredient Review deemed SLS to be safe for use in personal care products; the U.S. Environmental Protection Agency (EPA) considers it safe to eat from surfaces cleaned with products containing SLS; and the Food and Drug Administration (FDA) states SLS can be used as a food additive. That said, the amount of SLS and SLES used in shampoo is regulated and is therefore only present in the amount necessary to clean your hair which is different from the amount used to clean floors. 

Regarding cancer concerns, in addition to lack of substantial research linking SLS and SLES to increased cancer risk, SLS is not listed as a carcinogen by the International Agency for Research on Cancer (IARC). While cancer isn’t one of the possible harms of these particular sulfates, it’s important to note that skin irritation could be one of the side effects if the chemicals are too harsh for your skin. Before any new concerns bubble up, know that this adverse effect isn’t typically seen in most users of sulfate shampoos and generally only impacts those with a history of skin sensitivity or sulfate allergy. 

While research indicates that SLS and SLES aren’t cancer-causing ingredients, there are other carcinogenic ingredients to be mindful of in hair care products. The FDA has stated that formaldehyde is a carcinogen that’s been connected to both cancer and an abundance of other short- and long-term health concerns. It’s advised to stay away from products with formalin and methylene glycol as they often release or contain formaldehyde. Products that straighten hair are just one example of where these chemicals may be found. When thinking specifically about shampoos and cancer risks, dry shampoos often have the strongest link to cancer due to the ingredient benzene, which is a confirmed carcinogen. While a recall for products containing this cancer-causing chemical was issued in 2021, it’s suggested that people continue to check ingredients when purchasing haircare products as some products may still contain harmful ingredients. 

Ultimately, the decision to go sulfate-free is in your hands! Knowing that SLS and SLES aren’t currently linked to cancer, it’s up to you to decide if the potential skin irritation is a factor that’s still a concern. If you’re apprehension remains about hair care product ingredients, you might consider checking out more information from organizations like IARC, the National Cancer Institute, or the Cancer Fact Finder to learn more about the ingredients in the shampoos you’re browsing before you decide to buy.  

Wishing you plenty of cleansing and healthy showers,