Difference Between Sodium Lauryl Sulfate and Sodium Laureth Sulfate

The key difference between sodium lauryl sulfate and sodium laureth sulfate is that sodium lauryl sulfate is more irritating compared to sodium laureth sulfate.

Both sodium lauryl sulfate and sodium laureth sulfate are surfactants. They lower the surface tension of aqueous solutions, thereby, enhance the wetting of surfaces. Therefore, they are useful in cosmetic products such as soap, shampoo, shaving cream, mascara, moisturizer lotions, and sun cream. Also, they are in detergents, toothpaste, carpet cleaner, fabric glue, etc. In brief, they are important in these products because of their ability to remove oil and grease,  for being good foaming agents, and are very cheap. However, the key difference between sodium lauryl sulfate and sodium laureth sulfate arises because sodium laureth sulfate doesn’t dissolve proteins in the tissues like Sodium lauryl sulfate.

CONTENTS

1. Overview and Key Difference
2. What is Sodium Lauryl Sulfate
3. What is Sodium Laureth Sulfate
4. Side by Side Comparison – Sodium Lauryl Sulfate vs Sodium Laureth Sulfate in Tabular Form
5. Summary

What is Sodium Lauryl Sulfate?

Sodium lauryl sulfate or SLS has many synonyms, such as sodium dodecyl sulfate (SDS), lauryl sodium sulfate, lauryl sulfate sodium salt, sodium N- dodecyl sulfate, etc. The structural formula of this compound is CH₃-(CH₂)₁₁-O-SO₃-Na⁺. It is popular as a good cleaning agent, thus, included in various cleaning products and toiletries that we use. However, the laboratory experiments have proven that SLS is a skin irritant. It causes severe damage to the normal skin by disturbing its natural balance. Therefore, skin becomes permeable to other chemical substances. Sensitive skins are most easily damaged by SLS, and longer term usage can cause itchy, cracked dry skins. Further, it becomes toxic if enters in oral route.

Also, sodium lauryl sulfate causes eye irritations too. Because of the skin irritations, people avoid using products with sodium lauryl sulfate. Hence, sodium laureth sulfate has replaced this compound. Shampoos with SLS may increase hair falling, and it makes hair thin. Using toothpaste with SLS cause mouth ulcers. However, SLS is not carcinogenic. But, it can react with other chemicals in cosmetic products to produce nitrosamines which are carcinogenic.

Sodium lauryl sulfate is also an emulsifying and dispersing agent. Because of its emulsifying and thickening ability, we can use it as a food additive. Also, it is useful in the laboratories for nanoparticle preparation and for protein separation by electrophoresis (SDS—PAGE technique).

What is Sodium Laureth Sulfate?

The molecular formula of sodium laureth sulfate is CH₃-(CH2)₁₀-CH₂-(OCH₂CH₂)_n-O-SO₃Na⁺. It is popular as SLES in short form. Furthermore, this is also a surfactant and, therefore, useful for the same purposes as sodium lauryl sulfate. However, Sodium Laureth Sulfate is a less irritant than SLS.

Hence, manufacturers use SLES frequently in skin and hair products than SLS. Sodium Laureth Sulfate is not carcinogenic. However, when it gets contaminated with certain chemicals like ethylene oxide or 1,4- dioxane it can become carcinogenic.

What is the Difference Between Sodium Lauryl Sulfate and Sodium Laureth Sulfate?

Sodium lauryl sulfate is an organic compound having the chemical formula CH₃-(CH₂)₁₁-O-SO₃-Na⁺. Sodium laureth sulfate is also an organic compound but, having the chemical formula CH₃-(CH₂)₁₀-CH₂-(OCH₂CH₂)_n-O-SO₃Na⁺. The key difference between sodium lauryl sulfate and sodium laureth sulfate is that sodium lauryl sulfate is more irritating compared to sodium laureth sulfate. Hence, to avoid any skin irritations, the sodium lauryl sulfate in skincare products has been replaced by sodium laureth sulfate. Furthermore, as another important difference between sodium lauryl sulfate and sodium laureth sulfate, we can say that sodium lauryl sulfate can dissolve proteins in the tissues whereas sodium laureth sulfate doesn’t. This is the reason for the key difference between sodium lauryl sulfate and sodium laureth sulfate.

However, there are many uses of sodium lauryl sulfate such as a good cleaning agent, an emulsifying and dispersing agent, for nano particle preparation and for protein separation by electrophoresis whereas we can use sodium laureth sulfate as a component in skin and hair products, as a surfactant, etc.

Summary – Sodium Lauryl Sulfate vs Sodium Laureth Sulfate

The key difference between sodium lauryl sulfate and sodium laureth sulfate is that sodium lauryl sulfate is more irritating compared to sodium laureth sulfate. Therefore manufacturers tend to use sodium laureth sulfate rather than sodium lauryl sulfate in skincare products to avoid any skin irritations.

Reference:

1. “Sodium Laureth Sulfate.” American Chemical Society. Available here 
2. “Sodium Lauryl Sulfate.” National Center for Biotechnology Information. PubChem Compound Database, U.S. National Library of Medicine. Available here 

Image Courtesy:

1.”Sodium laurylsulfonate V.1″By Jü – Own work, (Public Domain) via Commons Wikimedia  
2.”Sodium laureth sulfate 2″By Mrgreen71 – Own work, (CC BY-SA 3.0) via Commons Wikimedia