Laureth-7 is a synthetic compound that functions as an emulsifier and surfactant in a variety of cosmetics and personal care products.
Laureth ingredients are synthesized through a process known as ethoxylation, a chemical reaction in which ethylene oxide is added to a substrate. In this case, the substrate is lauryl alcohol. Lauryl alcohol is obtained from lauric acid, a saturated fatty acid with a 12-carbon atom chain. It is obtained from palm kernel oil or coconut oil. The number associated with the laureth (i.e. laureth-7) indicates the average number of repeating ethylene oxide units in the molecule. Laureth-7 exists in the form of a clear, colorless liquid.
Laureth-7 functions as an emulsifier and surfactant in many different cosmetics and personal care products, including cream rinses, conditioners, bath oils, creams, lotions, deodorants, and shaving products.
Surfactant is the short term for surface active agent. Surfactants are compounds that lower the surface tension between two substances, such as two liquids or a liquid and a solid. In skin care products, surfactants work to degrease and emulsify oils and fats and suspend soil, allowing them to be washed away. This is possible because while one end of the surfactant molecule is attracted to water, the other end is attracted to oil. Thus, surfactants attract the oil, dirt, and other impurities that have accumulated on your skin during the day and wash them away. Due to these properties, laureth-7 can be found in many different cleansers and body washes.
The HLB value of laureth-7 is 12. HLB (Hydrophile-Lipophile Balance) is an empirical expression for the relationship of the hydrophilic (“water-loving”) and hydrophobic (“water-hating”) groups of a surfactant. Ingredients with HLB values greater than 10 are classified as water soluble.
Laureth-7 also functions as an emulsifier. An emulsifier is needed for products that contain both water and oil components, for example, when oils are added to a water-based formula. According to EFEMA, when water and oil are mixed together and vigorously shaken, a dispersion of oil droplets in water – and vice versa – is formed. When shaking stops, however, the two phases start to separate. To address this problem, an emulsifier can be added to the system, which helps the droplets remain dispersed and produces a stable emulsion.
As an emulsifier, laureth-7 consists of a water-loving hydrophilic head and an oil-loving hydrophobic tail. The hydrophilic head is directed to the aqueous phase and the hydrophobic tail to the oil phase. Once again, laureth-7 reduces the surface tension by positioning itself at the oil/water or air/water interface, which has a stabilizing effect on the emulsion.
The Cosmetic Ingredient Review (CIR) Expert Panel evaluated the scientific data and concluded that the laureth ingredients were safe as used in cosmetic products only when formulated to be non-irritating. This is because the laureth ingredients have the potential to irritate the skin.
Despite the approval of laureth-7 by the CIR Expert Panel, there are concerns about the presence of ethylene oxide in this ingredient. This is because the process of ethoxylation may lead to contamination with 1,4-dioxane, a potentially dangerous by-product. In fact, 1,4-dioxane is a known animal carcinogen that penetrates readily into the skin. This ingredient has also been linked with skin allergies.
The Organic Consumers Organization released a fact sheet on 1,4-dioxane based on information from the Campaign for Safe Cosmetics. The fact sheet outlines facts versus myths regarding 1,4-dioxane in personal care products. One concerning fact is that the levels of 1,4-dioxane found in many personal care products are 1,000 times higher than those found to cause cancer in animal studies. They add that according to the FDA, “Skin absorption studies demonstrated that dioxane readily penetrates animal and human skin from various types of vehicles.”
According to EWG, laureth-7 has received an overall rating of 3 on a 1 to 10 scale, with 1 being the lowest health hazard and 10 being the highest. Once again, the concerns for this ingredient are due to the potentially toxic impurities such as 1,4-dioxane.
The potential presence of 1,4-dioxane can be controlled through purification steps to remove it before blending laureth-7 into cosmetic formulations.
References: Technical Data Sheet Laureth-7, Wikipedia, “Dodecanol”, Paula’s Choice, “Surfactant”, Dow, “What is HLB?”, EFEMA, “What is an emulsifier?”, Cosmetics Info, “Laureth-7”, Organic Consumers Organization, “1,4-Dioxane and Cosmetic Safety”, Truth In Aging, “Laureth-7”, EWG’s Skin Deep Cosmetic Database, “Laureth-7”.