Ceteths are ingredients that belong to a class of compounds called alkyl PEG ethers, most of which function as surfactants in cosmetic products. Ceteth-20 is used in the formulation of hair dyes and colors, hair conditioners, permanent waves, and other hair care products, as well as makeup foundations, cleansing products, and other skin care products.
Origin
Alkaline catalysis is by far the most common method to manufacture alkyl PEG ethers, although acid catalysis is known. The initiation of the alkaline catalyzed synthesis of alkyl PEG ethers consists of the addition of ethylene oxide to a dry solution of the appropriate alcohol (e.g., cetyl alcohol is used to synthesize ceteths) with an alkali earth metal (e.g., potassium hydroxide) or alkoxide (e.g., sodium methoxide). The reaction continues to propagate (i.e., continues to add additional units of ethylene glycol to the alcohol) until the available ethylene oxide is consumed and/or the reaction is terminated by the addition of an acid (e.g., hydrochloric acid). Dioxane (1,4-diethylene dioxide; 1,4-dioxane) is commonly formed as a byproduct. Finally, a finishing step is commonly employed via the addition of one or more oxidizing agents (e.g., hydrogen peroxide) or antioxidants/stabilizers (e.g., butylated hydroxytoluene (BHT) or α-tocopherol (vitamin E).
Safety profile
The safety of Ceteth-1 to Ceteth-45 has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. The CIR Expert Panel evaluated the scientific data and concluded that Ceteth-1, -2, -3, -4, -5, -6, -10, -12, -14, -15, -16, -20, -24, -25, -30, and -45 were safe in the present practices of use. Ceteth-20 was found to enhance the transposition of a marker from phage l to bacterial DNA. Based on a study reporting nephrotoxicity in burn patients exposed to PEGs, the CIREP recommended that PEGs not be used on damaged skin.