Sterates are the salts and esters of steric acid, a saturated fatty acid with an 18-carbon chain. Steric acid is a waxy solid that occurs naturally in many animal and vegetable fats, though it is more common in the former. PEG 100 stearate is an ester, defined as chemical compound formed by the reaction between an acid and an alcohol; in this case, PEG 100 stearate is a water-soluble ester of polyethylene glycol (the PEG in PEG 100) and stearic acid. It can be formed by other esters with stearic acid as well. Often, natural oils, such as palm or coconut oil, combine with stearic acid to form PEG 100 stearate. Synthetically combining oxirane (ethylene oxide) and fatty acids can also create PEG 100 stearate. It is also known as carbowax, polywax, and lutrol. PEG stearate comes in other forms, with the number in the name representing the number of ethylene oxide monomers in the chain; this number can range from 2 to 150. Thus, PEG 100 stearate has more ethylene oxide monomers in the chain than the average PEG stearate.
Like other ingredients in the beauty and personal care industry, PEG 100 stearate has uses outside of the industry as well. The Food and Drug Administration has approved it as an indirect food additive, which means it becomes a part of the food in trace amounts during packaging, storing, and handling. As an indirect food additive, PEG 100 stearate works as a de-foaming agent; it is used to coat paper and cardboard in food packaging.
Outside of this specific use in the food industry, PEG 100 stearate is most popular as an ingredient in a range of beauty and personal care products. Its solubility and viscosity properties make it appealing in the beauty and personal care industry, explaining its popularity. PEG 100 stearate can be found in many products, including skin creams, conditioners, shampoos, body cleansers, and detergents. The primary use of PEG 100 stearate is as an emulsifier, which means it helps water and oil mix together in a range of products. For example, in shampoos and conditioners, PEG 100 stearate helps water mix with the oil and dirt in hair, allowing the buildup to be rinsed away. In this function, PEG 100 stearate functions as a cleansing agent.
PEG 100 stearate is also used as a surfactant in beauty and personal care products. In this role, PEG 100 stearate helps two ingredients that do not mix well combine better, allowing those ingredients to dissolve or disperse in one another. Thus, PEG 100 stearate can help the ingredients in beauty and personal care products combine appropriately, thus making them more effective.
Because it functions as an ingredient in food products and beauty and personal care products, PEG 100 stearate’s safety has been thoroughly studied. An April 2005 article in the journal Toxicity and Preclinical Affairs reported that PEG stearates produce little skin irritation and have “extremely low” toxicities. Because PEG stearates do not penetrate skin, few side effects are reported, according to the study composed by Claudia Fruijiter-Polloth. Likewise, research for the Cosmetic Ingredient Review Expert Panel confirms Fruijiter-Polloth’s study. The CIR Expert Panel ruled that PEG stearates, including PEG 100 stearate, are safe to use in cosmetics and personal care products. Other PEG stearates approved for such use include PEG 2, 6, 8, 12, 20, 32, 40, 50, and 150. The CIR Expert Panel’s most recent ruling was released in 2002. The Cosmetics Directive of the European Union approves the use of PEG stearates, including PEG 100 stearate, in beauty and personal care products as long as the stearic acid used comes from a plant.
Few side effects are associated with PEG 100 stearate when used in beauty and personal care products. However, it is recommended that PEG stearates are not applied to damaged skin; using the ingredient on skin that is cut or inflamed increases the risk of potential side effects, which are usually limited to skin irritation. Discontinuing use of the product featuring PEG 100 stearate is a simple way to eliminate any noted side effects. However, in the vast majority of users, PEG 100 stearate produces no noticeable side effects, simply making the products in which it is used more effective.