Ceteareth-12 is a synthetic compound that functions as an emulsifier and wetting agent in a variety of cosmetics and personal care products.
The group of ceteareth ingredients are synthetic compounds that are synthesized through a process known as ethoxylation, a chemical reaction in which ethylene oxide is added to a substrate. In regards to the ceteareth ingredients, there are two substrates: cetyl alcohol and stearyl alcohol, which are both naturally derived from coconut oil. The number associated with the ceteareth (i.e. ceteareth-12) indicates the average number of repeating ethylene oxide units in the molecule. There are a total of 32 different types of ceteareth ingredients.
In cosmetics and personal care products, ceteareth-12 functions as an emulsifier and wetting agent. It can be found in skin care products, hair conditioners, suntan and indoor tanning products, and hair dyes, colors, and tints.
As an emulsifier, ceteareth-12 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. This structure enables ceteareth-12 to reduce the surface tension by positioning itself at the oil/water or air/water interface, which has a stabilizing effect on the emulsion.
Ceteareth-12 has an HLB value of 13.5. HLB (Hydrophile-Lipophile Balance) is an empirical expression for the relationship of the hydrophilic and lipophilic groups of an emulsifier. An HLB greater than 10 means that the substance is soluble in water. High HLB emulsifiers such as ceteareth-12 give rise to oil-in-water emulsions.
Emulsifiers like ceteareth-12 are used in formulations that contain both water and oil components. Mixing water and oil together creates a dispersion of oil droplets in water (and vice versa). However, these two phases can separate if the product is left to settle. To address this problem, an emulsifier like ceteareth-12 can be added to the system to help the droplets remain dispersed. Emulsifiers improve the consistency of a product, which enables an even distribution of topical skin care benefits.
Ceteareth-12 also functions as a wetting agent. Wetting agents make products easier to spread and prevent the product from balling up on the surface of skin. This makes wetting agents useful ingredients for creams and lotions.
The safety of ceteareth-12 and the other ceteareth ingredients has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. The Panel evaluated the scientific data and noted that the ceteareth ingredients should not be used on damaged skin. This conclusion was based on research that kidney damage resulted when polyethylene glycol (PEG) ingredients were applied to the damaged skin of burn patients. Since ceteareth ingredients are the polyethylene glycol ethers of cetearyl alcohol, the Panel recommends avoiding use of ceteareth ingredients on damaged skin. Overall, the CIR Expert Panel concluded that the ceteareth ingredients were safe as used in cosmetics and personal care products.
Despite the approval of ceteareth-12 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. 1,4-dioxane is a known animal carcinogen that penetrates readily into the skin. According to the National Toxicology Program, “1,4-dioxane is reasonably anticipated to be a human carcinogen.” It has also been linked with skin allergies. However, the potential presence of 1,4-dioxane can be controlled through purification steps to remove it before blending ceteareth-12 into cosmetic formulations.
References: Wikipedia “Ethoxylation”, AOCS “An Introduction to Cosmetic Technology” 2015, Cosmetics Info “Ceteareth-12”, Organic Consumers Organization, “1,4-Dioxane and Cosmetic Safety”