In this article, we will try to explain, as in as much detail as possible, what Sodium Lauryl Sulfate (SLS) is, why SLS is added to a huge number of hygiene products, and what information we have about potential health issues that may arise when using this ingredient. We will also tell you what you can expect if you start using cosmetics that do not contain SLS.

What is Sodium Lauryl Sulfate (SLS) and why is it in my shampoo?

Sodium Lauryl Sulfate (SLS), better known as SLS, is an inexpensive cleansing agent added to a huge number of cosmetic and hygiene products such as shampoos, toothpastes, soaps, shower gels, laundry detergents, and so on. In its pure form, SLS is a white crystalline powder. Technically, it is a surfactant and an emulsifier.

Surfactants reduce the surface tension between two liquids, or between a liquid and a solid, to improve their interaction.

SLS also creates foam; this happens when SLS mixes with air as the cosmetic is applied to the body or hair. Foam is thousands of air bubbles. They form because the surface tension of the liquid is reduced, and water molecules can surround and “trap” air molecules, resulting in small bubbles. Therefore, foam by itself cannot clean your body or hair and is simply a by-product.

Emulsifiers, on the other hand, are molecules that have two different sides—a “head” and a “tail.” One side can bind with water but not with oily substances; the other side binds with oils but cannot bind with water.

Emulsifiers usually stabilize water and oily substances. This allows emulsifiers to bind the liquid with fats or oils and dirt on the skin and hair. Without emulsifiers, greasy and oily substances simply do not combine with liquid.

In summary: SLS enables molecules to interact effectively and helps remove dirt from the skin, hair, and teeth.

SLS may also be labeled as: Sodium Dodecyl Sulphate, Lauryl Sodium Sulphate, Sodium n-Dodecyl Sulphate, Lauryl Sulphate Sodium Salt.

WHAT’S THE ISSUE WITH SLS?

Panic or real concern?

While this ingredient helps cleansing agents work more effectively, a large number of people distrust products that contain SLS. After all, this substance irritates the skin and gums. In fact, SLS is often used as a control irritant when testing the effectiveness of skin-care products.

SLS is a skin-irritating substance, and there’s no arguing with that. But is SLS only an irritant? There are many suspicions that long-term use of products containing SLS or SLES (Sodium Laureth Sulfate) may pose a danger. At the same time, there are many opinions that it is absolutely safe. The truth is that there are well-founded concerns about the use of SLS, but we also have a lot of contentious information that is easy to refute.

Is SLS really made from coconut? Can this substance be called “natural”?

In fact, no. If you think about it, any substance has one or another degree of “naturalness.” It all depends on the process that makes a given chemical compound what it is. In the case of “coconut oil,” the end result is very far from “naturalness.”

Let’s break down the production process in simple terms:

  • Fatty acids are extracted from coconut oil.
  • Lauryl Alcohol is extracted from these acids.
  • Then Lauryl Alcohol is synthesized with Sulfur Trioxide Gas or Chlorosulfuric acid to obtain Sodium Lauryl Sulfate.

The extraction and synthesis processes are actually more detailed than described above, but for the purposes of this article this description is sufficient for the consumer to understand that the manufacturer is being crafty when describing cosmetics that contain SLS or SLES as “natural.” Sodium Lauryl Sulfate can be obtained both from coconut oil and from petroleum, which in no way affects the final product. Natural? It turns out not quite.

Can SLS cause cancer? 

Let’s take a step back and explain the origin of the assumptions and the link between SLS and cancer.
At the end of the 1980s in the USA, the spread of emails claiming that SLS causes cancer reached epidemic proportions. This was probably one of the first successful experiences of sending spam. The author of the letter claimed to work at the University of Pennsylvania, which lent plausibility to the message and attracted a lot of attention. This email turned out to be a fake, and the University of Pennsylvania stated that it had nothing to do with this message.

The letter was a fake, but the impression remained. And the talk about the potential danger of SLS continues to this day, especially regarding its link to cancer and danger to the central nervous system. Many people claim the issue is made up, but there is still a discussion about the “perception” of danger.
We want to describe the arguments both “for” and “against” the danger of SLS as a carcinogenic substance.


What do proponents of the view that SLS is potentially dangerous say?

Make no mistake, SLS has not been identified as a carcinogen! However, SLS is known as a substance that causes skin irritation. To combat these “irritating” properties for the skin, the substance ethylene oxide is very often added. As a result, a new chemical compound called Sodium Laureth Sulfate (SLES) appears. During this process, the resulting compound can be contaminated with dioxane, which is included on the list of potential carcinogens of the Environmental Protection Agency (USA). Ethylene oxide is considered potentially dangerous to the central nervous system, liver, kidneys, and eyes by the U.S. National Library of Medicine.

Thus, manufacturers of cosmetics that contain SLS can easily refute claims about a link between this substance and the occurrence of cancer. And the truth, to a large extent, depends on the manufacturing process. This means that the consumer must trust the cosmetics manufacturer, since there are no mandatory tests that products must pass before reaching store shelves.

Arguments of those who consider SLS a safe substance. 

While there is no dispute that SLS is a skin irritant, there are many people who defend SLS as an effective cleansing agent in personal hygiene products that poses no risk of causing cancer.

The American Cancer Council asserts that there is no link between the use of cosmetics containing SLS and cases of cancer. Manufacturers of “natural” and “organic” cosmetics “demonize” any chemical ingredients found in shampoos and toothpastes in order to promote their own “natural” products.

Many of those who oppose the use of Sodium Lauryl Sulfate also point to the fact that cancer incidence is rising and blame SLS and SLES for this. This would be a reasonable argument if not for the fact that it is not so. The truth is that in America the cancer rate has been steadily declining since 1988.

But some insist on the fact that SLS is also used in many industrial cleaning products, including engine degreasers and heavy-duty detergents. The fact is that many chemical compounds are used both in industry and in cosmetics, such as, for example, propylene glycol. The fact that these substances are used in industry does not mean they are dangerous. And conversely, a large number of “natural” substances can be considered dangerous; for example, tea tree oil is considered quite toxic in undiluted form.

Effect of long-term use of SLS 

One problem you’ll notice when reading articles devoted to sodium lauryl sulfate is the near-total lack of information about what effect the long-term use of SLS may have on the human body. There are many reasons for this. First, this type of research is very difficult to conduct, and second, any effect from using chemical compounds can be influenced by other chemicals.

As you probably know, most toothpastes and shampoos contain a large number of chemical ingredients, including cleansing agents such as SLS and SLES, preservatives, and pH stabilizers. The way these substances interact with one another can change how they affect our bodies.

Let’s look at what toxicology journals say about SLS:

Sodium lauryl sulfate is found to be safe with brief use, after which it is thoroughly rinsed off the skin with water. In products intended for longer contact with the skin, the concentration of SLS should not exceed 1%.

Unfortunately, you won’t be able to find the percentage content of the ingredients on the vast majority of cosmetic packaging. However, it is believed that in many shampoos the SLS level is significantly higher and can reach up to 20%. It is also inevitable that shampoo gets into the eyes when you wash your hair. Given the irritant properties of SLS and the sensitivity of the eyes, it is reasonable to assume that this substance has a negative effect on the eyes, especially in children.

There is well-founded concern due to the lack of knowledge about the long-term effects of using SLS.

What about swallowing toothpaste? ?

Toothpaste can also be absorbed, or we might even swallow it. In fact, swallowing SLS can cause nausea and diarrhea. It is well known that far fewer chemicals are absorbed through the skin than through the mucous membranes of the mouth.

The main concern is children’s dental hygiene. Children swallow toothpaste much more often than adults, especially given their curiosity and desire to learn about the world by grabbing things with their hands and tasting them. Regardless of your opinion about any link between SLS and cancer, this chemical negatively affects children’s stomachs. Fortunately, there are plenty of toothpastes that do not contain SLS.

The American College of Toxicology’s view on the effect of SLS on the eyes:
 In tests, a 10% concentration of Sodium Lauryl Sulfate caused corneal damage in rabbits if the substance was not rinsed with water or was rinsed with a delay. No damage occurred if the eyes were rinsed immediately after the chemical contacted the eye surface. A 5% concentration of SLS caused moderate irritation.

SLS and tests on animals 

It should be noted that products containing SLS or SLES may undergo animal testing at any stage. The subject of the research: the percentage content of SLS and its interaction with other product ingredients.

Evidence of this can be seen on the U.S. website of the Cosmetic Ingredient Review (CIR).

Although sodium lauryl sulfate is not a carcinogen, animal experiments have shown serious changes in the epidermis of mice in the area where SLS was applied.

Products that do not contain SLS

SLS Free Products

How do products that contain SLS and SLES differ for the buyer? First, you will notice a difference in the amount of foam—it will be significantly less; second, in the case of toothpaste, you will notice a difference in taste.
 As for toothpastes, you may need to experiment with several brands until you find the one that suits you best. It should not come as a surprise that children will initially be dissatisfied with the taste of SLS-free toothpaste.

Switching to SLS-free shampoos and shower gels may also take some getting used to. Most such shampoos and gels do not produce as much foam as shampoos and gels with sulfates. It may seem that your body and hair are not as clean. This is because sulfates strip your hair and skin of their naturally produced oils and dry out the skin—something that is often mistakenly perceived as a feeling of cleanliness.

Products that do not contain Sodium Lauryl Sulfate (SLS)

More and more manufacturers are producing products without SLS. Today these are not only shampoos and toothpastes, but also shower gels, soap, and even washing powder. Many people unconsciously buy SLS-free products by choosing packages labeled “Natural” and “Organic.” The truth is that these words are already used far too often.

The article was translated by SOLO-beauty in September 2025.

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