Compendium of the most significant studies with reference to properties, intake, effects.

Cornwell, P. A. (2018). A review of shampoo surfactant technology: consumer benefits, raw materials and recent developments. International journal of cosmetic science, 40(1), 16-30.

Abstract.  The purpose of this review was to assist the design of effective, modern, shampoo surfactant technologies. The mechanisms through which surfactants help deliver their effects are presented, along with the appraisal techniques through which surfactant options can be tested and screened for product development. 

Lockwood, A. P., Shun, P. K., Peakall, J., Warren, N. J., Barber, T., Basharat, N., ... & Hunter, T. N. (2021). Flotation using sodium dodecyl sulphate and sodium lauroyl isethionate for rapid dewatering of Mg (OH) 2 radwaste suspensions. RSC Advances, 11(30), 18661-18675.

Abstract. Mg(OH)2 suspensions were floated utilising sodium dodecyl sulphate (SDS) and sodium lauroyl isethionate (SLI) collectors, for rapid dewatering of radwaste suspensions.

Flood, J. C. (2015). Solution and Liquid Crystalline Properties of Sodium Lauroyl Methyl Isethionate/Water Mixtures. The University of Manchester (United Kingdom).

Abstract. Surfactants have characteristic structural features comprising a hydrophobic (water hating) tail group and hydrophilic head group (water loving).....

Jeraal, M. I., Roberts, K. J., McRobbie, I., & Harbottle, D. (2018). Process-focused synthesis, crystallization, and physicochemical characterization of sodium lauroyl isethionate. ACS Sustainable Chemistry & Engineering, 6(2), 2667-2675.

Abstract. A specific homologue, sodium lauroyl isethionate (SLI), was therefore synthesized, purified by recrystallization, and then subjected to a detailed physicochemical examination. 

Jeraal, M. I., Roberts, K. J., McRobbie, I., & Harbottle, D. (2019). Assessment of the thermal degradation of sodium lauroyl isethionate using predictive isoconversional kinetics and a temperature-resolved analysis of evolved gases. Industrial & Engineering Chemistry Research, 58(19), 8112-8122.

Abstract. Sodium lauroyl isethionate is a popular, milder alternative to traditional soaps and surfactants in personal care formulations. Product performance, efficiency, color, and odor, however, can be compromised by thermal degradation at elevated manufacturing temperatures. 

Belsito, D. V., Hill, R. A., Klaassen, C. D., Liebler, D. C., Marks Jr, J. G., Shank, R. C., ... & Snyder, P. W. (2013). Amended Safety Assessment of Isethionate Salts as Used in Cosmetics.

Abstract. The CIR Expert Panel concluded that the twelve isethionate salts listed below are safe in the present practices of use and concentration in cosmetics, when formulated to be non-irritating. This conclusion supersedes the earlier conclusion issued by the Expert Panel in 1993...Sodium Lauroyl Methyl Isethionate...

Sodium Lauroyl Methyl Isethionate is a mild surfactant derived from natural sources such as coconut oil or lauric acid. It is primarily used in skincare and haircare products for its cleansing properties, which gently remove dirt and impurities without irritating or drying out the skin. This ingredient is particularly appreciated in products for sensitive skin due to its ability to create a soft and creamy foam that leaves the skin and hair clean and hydrated.

Chemical Composition and Structure

Sodium Lauroyl Methyl Isethionate is a lauric ester of an isethionic acid derivative, neutralized with sodium to form an anionic surfactant. Its chemical structure provides excellent emulsifying and foaming properties, making it ideal for gentle cleansing formulations. The lauryl component is a 12-carbon chain that contributes to a silky and smooth feel on the skin.

The name defines the structure of the molecule:

• Sodium indicates the presence of a sodium ion in the compound. Sodium is often used in surfactants to improve their solubility in water.
• Lauroyl is derived from lauric acid, a saturated fatty acid with a chain of 12 carbon atoms. The suffix 'oyl' indicates that it is an acyl group, i.e. a functional group derived from an organic acid in which at least one -OH (hydroxyl) group is replaced by an -O-alkyl (alkoxy) group.
• Methyl indicates the presence of a methyl group (-CH3) in the compound.
• Isethionate is a sulphate group. It is derived from isethionic acid, which in turn is a derivative of ethylene oxide and sodium bisulphite.

Description of the raw materials used in its production:

• Methyl Isethionate: This is the starting material and is usually synthesized from isethionic acid.
• Fatty Acids: Specifically, lauric acid is the most common fatty acid used. It is derived from coconut oil or palm kernel oil.
• Sodium Hydroxide (NaOH): This is used to neutralize the reaction and produce the sodium salt form of the molecule.
• Catalysts: Certain catalysts might be used to expedite the esterification or the neutralization process.

Production Process

Sodium Lauroyl Methyl Isethionate is produced by reacting lauric acid (typically sourced from coconut oil) with methyl isethionate, followed by neutralization with sodium. This controlled chemical process results in a safe and mild surfactant with excellent cleansing and foaming properties. 

• Preparation of methyl isethionate. This compound can be synthesised by reacting methanol with isethionic acid. The reaction is carried out in the presence of a catalyst to accelerate the process.
• Activation of lauric acid. Lauric acid is converted into an active form, usually acyl chloride, which can react with methyl isethionate. This is usually done by reacting the lauric acid with a chlorinating agent. 
• Formation of sodium lauroyl methyl isethionate. Activated lauric acid (lauroyl chloride) is then reacted with methyl isethionate to form the desired product. This reaction takes place in an aprotic polar solvent and may require a base to neutralise the hydrochloric acid formed as a by-product.
• Purification. The final product is purified, usually through a process of extraction, washing and recrystallisation or distillation.

Physical Properties

It appears as a white powder or granules that are soluble in water. It has a slightly acidic pH, which is compatible with the skin’s natural pH, making it ideal for mild formulations. It produces a rich, creamy foam that leaves no residue and respects the skin’s hydrolipidic barrier, making it suitable for dry and sensitive skin types. 

What it is used for and where

Sodium Lauroyl Methyl Isethionate (SLMI) is a synthetic detergent commonly used in personal care products such as shampoos, body washes, and facial cleansers. It is known for its excellent foaming capabilities and mildness to skin, making it a popular choice in formulations where skin irritation can be a concern.

Cosmetics

Utilizzato in shampoo, saponi liquidi, prodotti da bano come tensioattivo schiumogeno di facile risciacquo, buone proprietà detergenti, debole sgrassaggio e lunga permanenza dell'effetto idratante.

Cleansing agent. Ingredient that cleanses skin without exploiting the surface-active properties that produce a lowering of the surface tension of the stratum corneum. 

Surfactant - Cleansing agent. Cosmetic products used to cleanse the skin utilise the surface-active action that produces a lowering of the surface tension of the stratum corneum, facilitating the removal of dirt and impurities. 

Commercial applications 

Shampoos. SLMI helps in removing dirt and oil from the hair, producing a rich lather.

Shower gels and liquid soaps. Due to its gentle nature, it's ideal for products meant for sensitive skin.

Facial products. SLMI can be found in facial cleansers due to its ability to gently cleanse the skin without drying it out.

Baby products. Its gentle formula makes it suitable for products meant for the sensitive skin of babies.

Foaming bath products. SLMI can be used in bath bombs and bath salts for its foaming capability.

Health and Safety Considerations

Safety in Use
Sodium Lauroyl Methyl Isethionate is generally considered safe for use in cosmetic products. It is known to be non-irritating to the skin and eyes, even at high concentrations. It is widely used in baby products and adult products for sensitive skin as it does not cause adverse effects.

Allergic Reactions
Allergic reactions to Sodium Lauroyl Methyl Isethionate are rare, and this surfactant is well tolerated even by people with sensitive or reactive skin. However, as with any cosmetic ingredient, it is always advisable to patch test the product on a small area of skin before use.

Toxicity and Carcinogenicity
It has been extensively tested for cosmetic use and is considered safe by major regulatory authorities, including the FDA and the European Union.

Environmental Considerations
As it is derived from plant-based sources like coconut oil, Sodium Lauroyl Methyl Isethionate is biodegradable and considered eco-friendly. It poses no significant environmental risks when disposed of properly, and its environmental impact is lower than that of synthetic or petroleum-based surfactants.

Regulatory Status
Sodium Lauroyl Methyl Isethionate is approved for use in cosmetics by major regulatory authorities, including the European Union and the FDA in the United States. It is widely used in skincare and haircare formulations globally

Sodium lauroyl methyl isethionate studies

Sodium Lauroyl 2-Methyl Isethionate:

• Molecular Formula  C₁₅H₂₉NaO₅S
• Molecular Weight     344.4
• CAS  928663-45-0
• UNII     II6VCD3S6R
• EC Number   700-150-3
• DSSTox Substance ID  DTXSID40892007
• IUPAC  sodium;2-dodecanoyloxypropane-1-sulfonate
• InChI=1S/C15H30O5S.Na/c1-3-4-5-6-7-8-9-10-11-12-15(16)20-14(2)13-21(17,18)19;/h14H,3-13H2,1-2H3,(H,17,18,19);/q;+1/p-1 
• InChl Key      NVIZQHFCDBQNPH-UHFFFAOYSA-M
• SMILES   CCCCCCCCCCCC(=O)OC(C)CS(=O)(=O)[O-].[Na+]
• MDL number  
• PubChem Substance ID    

Synonyms

• Sodium lauryl oxyethyl sulfonate
• Sodium lauroyl 2-methyl isethionate