Sodium Lauryl Sulfate and Sodium Laureth Sulfate

This inexpensive detergent is commonly used in cosmetic cleansers, hair shampoos, bath and shower gels, bubble baths, etc. – It is probably the most dangerous ingredient used in skin and hair-care products. In the cleaning industry SLS is used in garage floor cleaners, engine degreasers, car-wash soaps, etc. It is very corrosive and readily attacks greasy surfaces.

Sodium lauryl sulfate is used throughout the world for clinical testing as a primary skin irritant. Laboratories use it to irritate skin on test animals and humans so that they may then test healing agents to see how effective they are on the irritated skin.

A study at the University of Georgia Medical College, indicated that SLS penetrated into the eyes as well as brain, heart, liver, etc., and showed long-term retention in the tissues. The study also indicated that SLS penetrated young children’s eyes and prevented them from developing properly and caused cataracts to develop In adults.

May cause hair loss by attacking the follicle. Classified as a drug in bubble baths because it eats away skin protection and causes rashes and infection to occur.

Is potentially harmful to skin and hair. Cleans by corrosion. Dries skin by stripping the protective lipids from the surface so it can’t effectively regulate moisture.

Another extremely serious problem is the connection of SLS with nitrate contamination. SLS reacts with many types of ingredients used in skin products and forms nitrosomines (nitrates). Nitrates are potential cancer-causing carcinogenics.

Because of the alarming penetrating power of SLS, large amounts of these known carcinogens are absorbed through the skin into the body. A variation of SLS is SODIUM LAURETH SULFATE (Sodium Lauryl Ether Sulfate- SLES). It exhibits many of the same characteristics and is a higher-foaming variation of SLS.

Sodium lauryl sulfate

Not to be confused with Sodium laureth sulfate.

Sodium dodecyl sulfate

Sodium lauryl sulfate

Sodium lauryl sulfate (SLS), sodium laurilsulfate or sodium dodecyl sulfate (SDS or NaDS) (C12H25SO4Na) is an anionic surfactant used in many cleaning and hygiene products. The molecule has a tail of 12 carbon atoms, attached to a sulfate group, giving the molecule the amphiphilic properties required of a detergent.

SLS is a highly effective surfactant and is used in any task requiring the removal of oily stains and residues. For example, it is found in higher concentrations with industrial products including engine degreasers, floor cleaners, and car wash soaps. It is used in lower concentrations with toothpastes, shampoos, and shaving foams. It is an important component in bubble bath formulations for its thickening effect and its ability to create a lather.

SLS has not been proven to be carcinogenic when either applied directly to skin or consumed.[1] It has however been shown to irritate the skin of the face with prolonged and constant exposure (more than an hour) in young adults.[2] In a clinical study, SLS toothpaste was found to cause a higher frequency of canker sores than both cocoamidopropyl betaine or a detergent-free paste, on 30 patients with frequent occurrences of such ulcers.[3] However, another study comparing toothpastes with and without SLS found that it had no significant effect on ulcer patterns.[4]


Bottle of sodium dodecyl sulfate for use in the laboratory.

SLS is a highly effective surfactant and is used in any task requiring the removal of oily stains and residues. As such the compound is found in high concentrations in industrial products including engine degreasers, floor cleaners, and car wash soaps. In household products, SLS is used in lower concentrations with toothpastes, shampoos, and shaving foams. It is an important component in bubble bath formulations for its thickening effect and its ability to create a lather.

Research suggests that SLS could represent a potentially effective topical microbicide, which can also inhibit and possibly prevent infection by variousenveloped and non-enveloped viruses such as the Herpes simplex viruses, HIV, and the Semliki Forest Virus.[5][6]

It has recently found application as a surfactant in gas hydrate or methane hydrate formation reactions, increasing the rate of formation as much as 700 times.[7]

In medicine, sodium lauryl sulfate is used rectally as a laxative in enemas, and as an excipient on some dissolvable aspirins and other fiber therapy caplets.

Sodium lauryl sulfate is increasingly found in all kinds of common over-the-counter orally ingested drugs like aspirin as well as prescription medicines like drugs for heart problems. The reason for this is that it aids the production process by helping tablets not to stick to the mould when pressed into shape. The long term health implications of this for patients has not been the subject of any studies, and in the UK for instance it is now virtually impossible to get aspirin of any brand, standard or dispersible that does not contain sodium lauryl sulfate.

It can be used to aid in lysing cells during DNA extraction and for unraveling proteins in SDS-PAGE. Sodium lauryl sulfate, in science referred to as sodium dodecyl sulfate (SDS), is commonly used in preparingproteins for electrophoresis in the SDS-PAGE technique.[8] This compound works by disrupting non-covalent bonds in the proteins, denaturing them, and causing the molecules to lose their native shape (conformation). Also, anions of SDS bind to the main peptide chain at a ratio of one SDS anion for every two amino acid residues.[citation needed] This effectively imparts a negative charge on the protein that is proportional to the mass of that protein (about 1.4 g SDS/g protein).

This new negative charge is significantly greater than the original charge of that protein. The electrostatic repulsion that is created by binding of SDS causes proteins to unfold into a rod-like shape thereby eliminating differences in shape as a factor for separation in the gel. Sodium lauryl sulfate is probably the most researched anionic surfactant compound. Like all detergent surfactants (including soaps), sodium lauryl sulfate removes oils from the skin, and can cause skin and eye irritation. The critical micelle concentration (CMC) in pure water at 25°C is 0.0082 M,[9] and the aggregation number at this concentration is usually considered to be about 62.[10] The micelle ionization fraction (α) is around 0.3 (or 30%).[11]

There is evidence that surfactants such as sodium lauryl sulfate can act as a shark repellent at concentrations on the order of 100 parts per million. However, this does not meet the desired "cloud" deterrence level of 0.1 parts per million. [12] [13]


Sodium lauryl sulfate structure 

SLS is synthesized by reacting lauryl alcohol with sulfuric acid to produce hydrogen lauryl sulfate which is then neutralized through the addition of sodium carbonate.[14] Lauryl alcohol is in turn usually derived from eithercoconut or palm kernel oil by hydrolysis, which liberates their fatty acids, followed by reduction of the acid group to an alcohol.

Due to this synthesis method, SLS is actually not pure dodecyl sulfate but a mixture of alkyl sulfates with dodecyl sulfate as the main component.[15]



SLS has not been proven to be carcinogenic when either applied directly to skin or consumed.[1] SLS however is a strong surfactant and some dermatological concerns regarding its role as an irritant have been raised in published reports.[16]


SLS may worsen skin problems in individuals with chronic skin hypersensitivity, with some people being affected more than others.[17][18][19] SLS has also been shown to irritate the skin of the face with prolonged and constant exposure (more than an hour) in young adults.[2] In animal studies SLS appears to cause skin and eye irritation.[16]

Canker sores

A preliminary study suggested SLS in toothpaste caused the recurrence of aphthous ulcers, commonly referred to in some countries as canker sores or white sores.[20] The preliminary study "showed a statistically significant decrease in the number of aphthous ulcers from 14.3 after using the SLS-containing dentifrice to 5.1 ulcers after brushing with the SLS-free dentifrice."[20] A clinical study comparing the incidence of recurrent aphthous ulcers during the use of dentifrices with and without sodium lauryl sulfate supported the findings of an earlier independent study which suggest that use of an SLS-free dentifrice should be considered for individuals who suffer from recurrent aphthous ulcers.[21] A clinical double-blind crossover study found sodium lauryl sulfate had a significantly higher frequency of aphthous ulcers than both cocoamidopropyl betaine or a detergent-free paste, on 30 patients with frequent occurrences of recurrent aphthous ulcers.[3] The clinical double-blind crossover study suggests use of an SLS-free toothpaste for patients with recurrent aphthous ulcers would reduce recurrence.[3] A double blind crossover trial comparing toothpastes with and without SLS found that it had no significant effect on ulcer patterns.[4]

Sodium laureth sulfate

Not to be confused with Sodium lauryl sulfate.

Sodium laureth sulfate


Sodium laureth sulfate, or sodium lauryl ether sulfate (SLES), is a detergent and surfactant found in many personal care products (soaps, shampoos, toothpaste etc.). SLES is an inexpensive and very effective foaming agent.[1]

Chemical structure

Its chemical formula is CH3(CH2)10CH2(OCH2CH2)nOSO3Na. Sometimes the number represented by n is specified in the name, for example laureth-2 sulfate. The commercial product is heterogeneous in the number of ethoxyl groups, where n is the mean. It is common for commercial products for n= 3. SLES is prepared by ethoxylation of dodecyl alcohol. The resulting ethoxylate is converted to an half ester of sulfuric acid, which is neutralized by conversion to the sodium salt.[1] The related surfactant sodium lauryl sulfate (also known as sodium dodecyl sulfate or SLS) is produced similarly, but without the ethoxylation step. SLS and ammonium lauryl sulfate (ALS) are commonly used alternatives to SLES in consumer products.[1]


SLES, SLS and ALS are surfactants that are used in many cosmetic products for their cleansing and emulsifying properties. They behave similarly to soap.



Although SLES is considered safe at the concentrations used in cosmetic products, at higher concentrations it is an irritant similar to other detergents.[2] SLES has been shown to produce eye or skin irritation in experimental animals and in some human test subjects.[2] The related surfactant SLS is a known irritant,[3][4] and research suggests that SLES can also cause irritation after extended exposure in some people.[5][6]


Toxicology research by the OSHA, NTP, and IARC supports the conclusions of the Cosmetic, Toiletry, and Fragrance Association (CTFA) and the American Cancer Society that SLES is not a carcinogen.[7] The U.S. Environmental Protection Agency classifies 1,4-dioxane to be a probable human carcinogen (having observed an increased incidence of cancer in controlled animal studies, but not in epidemiological studies of workers using the compound), and a known irritant (with a no-observed-adverse-effects level of 400 milligrams per cubic meter) at concentrations significantly higher than those found in commercial products.[8] Under Proposition 65, 1,4-dioxane is classified in the U.S. state of California to cause cancer.[9][10]

1,4-Dioxane contaminant

Some products containing SLES have been found to contain low levels of the known carcinogen 1,4-dioxane, with the recommendation from the U.S. Food and Drug Administration that these levels be monitored.[11] The FDA encourages manufacturers to remove 1,4-dioxane, though it is not required by federal law.[12]

Keys Banned Chemical Series – SLS (Sodium Laureth Sulfate)

January 19th, 2010

Dirty Dozen Chemicals: SLS

Bob Root, Keys CTO

By Bob Root

Keys Technologist

Many people that I meet ask me to describe why I do not use certain chemicals.  I tell them that my reasons are practical not political.  I generally explain in three to five pragmatic reasons why I do not use certain ingredients.  Most encourage me to offer my simplified reasons, so I am beginning to undertake why we do not use certain ingredients.  In this series of article, I will start with the Dirty Dozen.

SLS Overview:

Sodium Laureth Sulfate (SLS) is the first chemical listed on the Dirty Dozen Chemicals created by the Marin County Cancer Project.  These Dirty Dozen have been linked to elevated Cancer rates in people and their pets.

SLS has over 200 synonyms listed on the National Institutes of Health Toxnet.  Some very chemical sounding while other sound very safe and botanical.  They are fundamentally the same.  We believe that many manufacturers have chosen to create synonyms to claim that they do not use SLS.

SLS is used in cleansers, soaps, shampoos and even toothpaste.  It makes things suds, degreases and cleans.  It was introduced into the US after World War II as an engine degreaser.  Up until the 50’s it was used primarily for that purpose in the form of a product called Gunk!  Gunk is an engine degreaser that is still sold in auto parts stores to get rid of engine grime.

Companies started to use SLS in personal care products to make then foam the same in hard and soft water.  As the use grew, it became very inexpensive which broadened its appeal to companies wanting cleaning degreasing action.  Most recently, companies making “patch” based products for non-smoking or weight loss have found that SLS also help to deliver the active ingredients deeply and faster.  This is sort of the main rub I have with the ingredient, but it is only just one of the things that keeps me from using the ingredient.

Recently, Fenchem Company has published some papers that link SLS in shampoos to baldness.  This is something that we have suspected and known for quite a few years.

Why Keys Does Not Use SLS

In all the yelling and screaming about what is safe and not, I have developed a series of reasons that I do not use the Dirty Dozen Chemicals as well as others.  I have chosen this format to simplify my reasons for our customers.  When I am speaking and arguing with others in the industry my basis is much more technical.  I have chosen to over simplify my reasons here to help lay people understand my reasoning.

Reason #1  Inflammation from SLS

Chemical Inflammation aka burns!

I do not use SLS or any family of SLS surfactant because of the reactions I see with the skin.  Generally, anywhere above 0.5% of SLS, we see inflammation of the skin.  The above comment from Fenchem as bee well known to us for quite a few years, but without clinical studies, it would only be opinion and comment.  We see what they see all over the body, but it tends to manifest itself with early male pattern baldness.  What we believe is that the SLS causes inflammation of the hair follicles and causes them to close down starving off the hair growth.  We have noticed for years that men that stop using SLS based shampoos and start using Island Rx have seen renewed hair growth.  We believe it is mostly due to the switch from SLS based shampoos.  In many cases, to be an effective surfactant, SLS needs to be around 15% or higher.  This level has shown mild to severe inflammation for areas like the soft tissue around the eyes to even tougher skin on the arms and legs.  The inflammation seems to be cumulative, but reverses quickly when SLS is removed from the person regime.  Sometimes in science, taking something away results in more research facts than introducing a substance.  This is especially true when the effects of a chemical seem to be more gradual and effect other differently.

Reason #2  Stripping of Natural Oils caused by SLS

As we said, SLS began as an engine degreaser after World War II.  Even in amounts as low as 1%, SLS seems to over-clean and remove the skins natural oils.  Madison Avenue convinced us that our skin should not have any oil on it which is totally false.  Our natural oils are much of what retain our natural skin youthfulness.  In fact we believe that it is a combination of stripping these oils and unnatural dehydration caused by SLS causes skin to lose its luster.  This is why we use pharmaceutical grade natural oils in our products.  Think of it as repairing.

Skin Layers

Reason #3  Increased Skin Permeability caused by SLS

Many companies using patch therapies and many pharmaceutical products  contain SLS to increase to how it aids to penetrate the skin and small intestines.  We extrapolate that SLS in skin care products helps to increase permeability allowing hydrocarbons, bacteria, yeast and other pollutants into the skin.

Reason #4  Cellular Breakdown

In some recent test, we have seen thinning of the skin cellular wall below the epidermis in the dermal level.  The outer layer of the skin has 25 to 30 layers of dead skin cells.  Below that are living cells whose cell wall seem to be effected by SLS.  The critical word here is “seems.”  We are just beginning to look at this closer, but ”seems” is good enough for me when I add the other three primary reason

Please send me your questions and comments,  Bob Root

For those of you that want more opinion, the following description is from The Natural Health Information Center offered as their description of SLS.  This is not Keys opinion, but we do agree with much of their findings and comments

Both Sodium Laureth Sulfate (SLES) and its close relative Sodium Lauryl Sulfate (SLS) are commonly used in many soaps, shampoos, detergents, toothpastes and other products that we expect to “foam up”. Both chemicals are very effective foaming agents, chemically known as surfactants.

Unfortunately, both sodium laureth sulfate and its cousin are also very dangerous, highly irritating chemicals. Far from giving “healthy shining hair” and “beautiful skin”, soaps and shampoos containing sodium laureth sulfate can lead to direct damage to the hair follicle, skin damage, permanent eye damage in children and even liver toxicity.

Although sodium laureth sulfate is somewhat less irritating than SLS, it cannot be metabolized by the liver and its effects are therefore much longer-lasting. This not only means it stays in the body tissues for longer, but much more precious energy is used getting rid of it.

A report published in the Journal of The American College of Toxicology in 1983 showed that concentrations of SLS as low as 0.5% could cause irritation and concentrations of 10-30% caused skin corrosion and severe irritation. National Institutes of Health “Household Products Directory” of chemical ingredients lists over 80 products that contain SLS and SLES. Some soaps have concentrations of up to 30%, which the ACT report called “highly irritating and dangerous“.

Shampoos are among the most frequently reported products to the FDA. Reports include eye irritation, scalp irritation, tangled hair, swelling of the hands, face and arms and split and fuzzy hair. This is highly characteristic of sodium laureth sulfate and almost definitely directly related to its use.

Click here to learn of the possible health effects of sodium laureth sulfate

So why is a dangerous chemical like sodium laureth sulfate used in our soaps and shampoos?

The answer is simple – it is cheap. The sodium laureth sulfate found in our soaps is exactly the same as you would find in a car wash or even a garage, where it is used to degrease car engines.

On the same way as it dissolves the grease on car engines, SLES also dissolves the oils on your skin, which can cause a drying effect. It is also well documented that itdenatures skin proteins, which causes not only irritation, but also allows environmental contaminants easier access to the lower, sensitive layers of the skin.

This denaturing of skin proteins may even be implicated in skin and other cancers.

Perhaps most worryingly, sodium laureth sulfate is also absorbed into the body from skin application. Once it has been absorbed, one of the main effects of SLS is to mimic the activity of the hormone Oestrogen. This has many health implications and may be responsible for a variety of health problems from PMS and Menopausal symptoms todropping male fertility and increasing female cancers such as breast cancer, where oestrogen levels are known to be involved.

Products commonly found to contains SLS or Sodium Laureth Sulfate

Tooth paste
Washing-up liquid / dish soap
Laundry detergent
Children’s soaps / shampoos
Stain Remover
Carpet Cleaner
Fabric glue
Body wash
Shave cream
Skin cleanser
Moisture lotion / Moisturizer
Sun Cream

The use of sodium laureth sulfate in children’s products is particularly worrying. It is known that, whether it gets in the eyes or not, skin application DOES lead to measurable concentrations in the eyes of children. This is known to affect eye development, and the damage caused in this manner is irreversible. If you have children DO NOT USE products containing sodium laureth sulfate or SLS – they will thank you for it one day.

Do not believe that just because a product is labeled as “natural” it is free from SLS or sodium laureth sulfate. Most common brands of “Natural” or “Herbal” shampoos and cleansers still use these harmful chemicals as their main active ingredient – check your labels!

That is not to say that you can’t get sodium laureth sulfate-free shampoos, soaps, detergents and toothpastes. Some highly reputable companies have been producing such products for years. These products not only contains no sodium laureth sulfate, they are also free of other harmful chemical colorings, preservatives and even flavorings.