Key information
SLS (sodium lauryl sulfate) is an anionic surfactant with strong cleansing and foaming properties, used for decades.
It is approved as safe by the CIR, FDA, and European regulatory authorities at permitted concentrations.
However, it may cause irritation in people with sensitive skin, which is why milder alternatives have been developed.
The controversy surrounding SLS mainly results from misinformation - it is not carcinogenic or toxic when used as intended.
Sodium lauryl sulfate (SLS) is one of the most commonly used and, at the same time, one of the most controversial cosmetic ingredients. You can find it in shampoos, toothpastes, and shower gels. Many myths have arisen around it, although there are also justified concerns. In this article, we present the facts - what SLS is, how it works, and who it may not be suitable for.
What is SLS - chemical structure and basic properties
SLS (short for Sodium Lauryl Sulfate) is an anionic surfactant with the chemical formula C₁₂H₂₅NaO₄S. It consists of a 12-carbon alkyl chain (the hydrophobic part) connected to a sulfate group (the hydrophilic part).
Thanks to this amphiphilic structure, SLS is excellent at reducing the surface tension of water. It enables fat to mix with water and effectively removes impurities. It creates abundant, stable foam, and this is a feature particularly valued in cleansing products.
SLS is produced from lauric acid, which is obtained from coconut oil or palm oil. Despite the plant-based origin of the raw material, it is a synthetic ingredient because it undergoes chemical processes such as sulfation and neutralization.
How does SLS work as a surfactant?
SLS belongs to anionic surfactants - the most effective group in terms of cleansing properties. Its mechanism of action is based on the formation of micelles, which surround particles of dirt and grease.
The properties of SLS in formulations include:
strong cleansing action - it effectively removes sebum, dirt, styling residue, and environmental pollutants. It is one of the most efficient surfactants in this respect;
abundant foam - it creates dense, stable foam even at low concentrations. Consumers still associate foam with cleansing effectiveness;
good wetting properties - it facilitates the spreading of the product on the skin and hair;
low cost - it is one of the cheapest surfactants, which reduces production costs.
Uses of SLS in cosmetics and industry
SLS is used wherever effective cleansing and abundant foam are desired. Below, we present the main areas of use of this surfactant, namely cosmetics and industry.
Cosmetics
In shampoos, SLS is responsible for removing sebum and styling residue. In shower gels and liquid soaps, it ensures thorough skin cleansing. In toothpastes, it creates foam and supports the removal of dental plaque. It is also used in shaving foams and makeup removal products.
Industry
In detergents and cleaning agents, SLS removes grease and organic dirt. It is used as an emulsifying agent in industrial processes. It is also used in floor cleaners, car wash products, and industrial surface cleaning products.
The controversy around SLS - facts versus myths
SLS triggers emotions like few other cosmetic ingredients. Some concerns are justified, but much of the information circulating online is misinformation. Here is a comparison of facts and myths.
Claim |
Truth or myth? |
Explanation |
SLS is carcinogenic |
MYTH |
There is no scientific evidence. The IARC does not classify SLS as a carcinogen. |
SLS irritates the skin |
FACT |
It may cause irritation, especially in people with sensitive skin or at high concentrations. |
SLS is toxic |
MYTH |
At the concentrations used in cosmetics, it is safe. Toxicity applies only to concentrated forms. |
SLS damages eyesight |
PARTIAL FACT |
Contact with the eyes causes irritation, but not permanent damage. For this reason, products with SLS must contain appropriate warnings. |
SLS causes hair loss |
MYTH |
There is no scientific evidence. It may dry out the hair, but it does not affect hair follicles. |
Where did the controversy come from? In the 1990s, false information supposedly originating from scientific institutions became widespread. These were so-called email chain messages with no basis in research. Unfortunately, these myths persist to this day.
SLS safety - what do studies and institutions say?
SLS is one of the best-studied cosmetic ingredients. The main institutions dealing with cosmetic safety have issued clear opinions about it.
CIR (Cosmetic Ingredient Review) - the American expert panel recognized SLS as safe at concentrations up to 1% in leave-on products and higher in rinse-off products. It recommends limiting contact time with the skin.
SCCS (Scientific Committee on Consumer Safety) - the European scientific committee confirms the safety of SLS in cosmetic products when used appropriately.
FDA - the American agency permits SLS as an ingredient in cosmetics and oral hygiene products.
The actual adverse effect is skin irritation, especially with prolonged contact or in people with a weakened skin barrier, for example due to eczema, atopic dermatitis, or psoriasis. This does not mean that SLS is dangerous - it means that it is not suitable for everyone.
Alternatives to SLS - when is it worth replacing this ingredient?
For people with sensitive skin or those who prefer milder ingredients, there are effective alternatives. Here is a comparison of the most popular substitutes for SLS.
SLES (Sodium Laureth Sulfate) - an ethoxylated version of SLS, much milder while maintaining good cleansing properties. The most common alternative in shampoos.
Cocamidopropyl Betaine - an amphoteric surfactant, very mild. Often used in combination with SLES as a soothing ingredient. A base surfactant in children's cosmetics.
Alkyl glucosides - nonionic surfactants of plant origin (coco glucoside, decyl glucoside). Very mild, biodegradable, accepted in natural cosmetics.
Sulfosuccinates - mild anionic surfactants, well tolerated by sensitive skin. Used in hypoallergenic products and products for infants.
When should you replace SLS? When you have sensitive, dry, or atopic skin, notice irritation after using products with SLS, or if you prefer natural or eco-friendly cosmetics.
SLS in cosmetics - an informed choice instead of fear
Sodium lauryl sulfate is an effective, well-studied surfactant that safely serves millions of consumers. It is not carcinogenic or toxic - these are scientifically confirmed facts. However, it may irritate sensitive skin, which is a justified reason to choose alternatives. The most important thing is an informed decision based on facts, not internet myths.
FAQ - frequently asked questions
Is SLS banned in the European Union?
No. SLS is fully permitted for use in cosmetics in the EU. It is not on the list of prohibited or restricted substances in the Cosmetics Regulation. Restrictions apply only to concentrations in certain products.
Who is SLS not suitable for?
SLS may not be suitable for people with sensitive, dry, or atopic skin, as well as for people with eczema or psoriasis. If you notice redness, itching, or dryness after using products with SLS, consider milder alternatives.
Are SLS and SLES the same thing?
No. SLES (Sodium Laureth Sulfate) is an ethoxylated version of SLS. The ethoxylation process makes SLES milder for the skin while maintaining good cleansing properties. These are two different ingredients with different safety profiles.
At what concentration is SLS safe?
In rinse-off products (shampoos, gels), SLS is safe at concentrations up to a dozen or so percent with short contact time. In leave-on products, concentrations up to 1% are recommended. As you can see, exposure time is important here.
Is SLS in toothpaste safe?
Yes, SLS in toothpaste is safe at the concentrations used (approx. 1-2%). However, it may cause irritation of the mucous membrane in some people. If you have recurrent aphthous stomatitis, consider choosing an SLS-free toothpaste.