Difference Between Sodium Lauryl Sulfate and Sodium Laureth Sulfate

Sodium Lauryl Sulfate vs 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 used in cosmetic products such as soap, shampoo, shaving cream, mascara, moisturizer lotions, and sun cream, also in detergents, toothpastes, carpet cleaner, fabric glue, etc. Moreover, they are used in these products because of their ability to remove oil/grease, they are also good foaming agents, and are very cheap. Both the chemicals are esters of sulfuric acid. Because of the ionic group, there is a hydrophilic end, and the hydrocarbon chain is hydrophobic. Therefore, the two molecules are amphiphilic. This property allows them to dissolve in oil and water simultaneously. That is, the hydrophobic end dissolves the oil, while the hydrophilic part interacts with water.

Sodium Lauryl Sulfate

Sodium lauryl sulfate, which is also known as 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 is CH3-(CH2)11-O-SO3-Na+. It is known to be 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. It will be toxic if enters in oral route. It is also proven that sodium lauryl sulfate cause eye irritations too. Because of the skin irritations, people avoid using products with sodium lauryl sulfate, and it is replaced with sodium laureth sulfate. Shampoos with SLS may increase hair falling, and it makes hair thin. Using toothpastes with SLS cause mouth ulcers. SLS is not carcinogenic. However, it can react with other chemicals in cosmetic products to produce nitrosamines which can be carcinogenic.

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

Sodium Laureth Sulfate

The molecular formula of sodium laureth sulfate is CH3-(CH2)10-CH2-(OCH2CH2)n-O-SO3Na+ . It is known as SLES in short form. This is also a surfactant, therefore, used for the same purposes as sodium lauryl sulfate. However, Sodium laureth sulfate is a less irritant than SLS, hence, SLES is now frequently used in skin and hair products than SLS. Sodium laureth sulfate is not carcinogenic. However, when it is contaminated with certain chemicals like ethylene oxide or 1,4- dioxane it can be carcinogenic.

What’s the difference between Sodium Lauryl Sulfate and Sodium Laureth Sulfate?

- Sodium laureth sulfate is less irritating than sodium lauryl sulfate. This is because Sodium laureth sulfate doesn’t dissolve proteins in the tissues like Sodium lauryl sulfate.

- Sodium laureth sulfate has a higher molecular weight than sodium lauryl sulfate.