Ceteareth-20 is a synthetic compound that functions as an emulsifier and surfactant 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-20) indicates the average number of repeating ethylene oxide units in the molecule. There are a total of 32 different types of ceteareth ingredients.
Ceteareth-20 functions as a surfactant and an emulsifier in many different cosmetics and personal care products, including facial moisturizers, anti-aging treatments, conditioners, cleansers, sunscreens, exfoliants, and acne treatments.
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, ceteareth-20 can be found in many different cleansers and body washes.
Ceteareth-20 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, ceteareth-20 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, ceteareth-20 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 ceteareth ingredients were safe as used in cosmetic products. The CIR Expert Panel noted that 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 CIR Expert Panel recommends avoiding use of ceteareth ingredients on damaged skin.
Despite the approval of ceteareth-20 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, ceteareth-20 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 ceteareth-20 into cosmetic formulations.
References: Wikipedia, “Ethoxylation”, Truth In Aging, “Ceteareth-20”, Paula’s Choice, “Surfactant”, EFEMA, “What is an emulsifier?”, Cosmetics Info, “Ceteareth-20”, Int J Toxicol 18(3):41-49 · April 1999 , Organic Consumers Organization, “1,4-Dioxane and Cosmetic Safety”, EWG’s Skin Deep Cosmetic Database, “Ceteareth-20”.