What Is Stearic Acid?
Stearic acid is a saturated fatty acid with an 18 carbon chain that is used in a variety of cosmetics and skincare products. Stearic acid is mainly used to support the scent of the product and improve the texture and spreadability. Stearic acid also has an added benefit as it helps to improve the moisture content of the skin.
Stearic acid, also known as octadecanoic acid, can be derived from both animal and vegetable fats and oils. However, fats and oils rich in stearic acid are more abundant in animal fat, up to 30%, than in vegetable fat, typically less than 5%. Depending on the source of the stearic acid it can be a vegan ingredient, particularly when it is derived from either cocoa or shea butter which have a higher stearic acid content of 28 to 45% respectively.
the good:Helps to improve the scent, texture, and spreadability of a formulation. Stearic acid also has an added benefit as it helps to improve the moisture content of the skin.
the not so good:Depending on the source of the stearic acid it can be vegan or animal-derived.
Who is it for?All skin types except those that have an identified allergy to it.
Synergetic ingredients:Works well with most ingredients
Keep an eye on:If you are looking to use a vegan product check which source of stearic acid the brand uses.
What Is The Difference Between Acids And Fatty Acids?
Despite having acid in their name, fatty acids are very different from acids. Fatty acids are the building blocks for fats and oils. Unlike acids, they tend to be hydrating and gentle on the skin.
What Are The Benefits of Stearic Acid In A Formulation?
Stearic acid functions mainly as a surfactant, emulsifier, and thickener when added to cosmetics and skincare products.
Surfactant is the short term for surface active agent. Surfactants are compounds that lower the surface tension between two substances to help them mix or allow the skin to be wet evenly.
Another job of surfactants is to degrease and emulsify oils and fats and suspend dirt, 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, stearic acid can be found in many different cleansers and body washes.
Stearic acid also acts as an emulsifier. An emulsifier is needed for products that contain both water and oil components. Water and oil-based ingredients tend to separate in the formulation. Emulsifiers help to keep them mixed and prevent the splitting or separating of ingredients. This helps to stabilize and improve the longevity of your product.
As an emulsifier, stearic acid consists of a water-loving hydrophilic head and an oil-loving hydrophobic tail. The hydrophilic head is attracted to the water-based ingredients and the hydrophobic tail to the oil-based ingredients, pulling them together and preventing that separation.
Another property of stearic acid is its ability to function as a thickener or hardener. This is why stearic acid is added to things like soaps, candles, plastics, oil pastels, etc. It helps to harden the product and also helps to retain its shape.
How Does Stearic Acid Benefit The Skin?
As a surfactant, stearic acid helps to wash away excess oil and dirt from the skin. Stearic acid attracts dirt and oils and allows them to be rinsed from the skin.
Stearic acid has been shown to protect the skin’s natural barrier against water loss and help support the skin’s protective barrier. The skin’s natural barrier consists of the first few layers of skin and the natural oils that it produces. This barrier protects the skin from allergens, bacteria, and from losing water to the air and environment. When the skin barrier is damaged or disrupted through the use of harsh products, aging, the environment or skin conditions such as eczema or dermatitis, the skin can lose this protective ability.
Stearic acid is an important component in the skin’s barrier and is a widely used in skincare products. In formulations in may support the healthy functioning of the skin barrier, potentially helping to improve hydration and sensitivity. It is important to note that this benefit has not been well researched.
Is Stearic Acid Safe?
The US Food and Drug Administration includes stearic acid on its list of direct food additives considered Generally Recognized As Safe (GRAS). The Cosmetic Ingredient Review Expert Panel, a group responsible for evaluating the safety of skincare and cosmetic ingredients, evaluated the scientific data, and concluded that stearic acid is safe for use in cosmetic products.
References:Lin, T, Zhong, L, & Santiago, J, 2017. ‘Anti-Inflammatory and Skin Barrier Repair Effects of Topical Application of Some Plant Oils’, International Journal of Molecular Sciences, 19(1), 70.
Cosmetic Ingredient Review, 1987. ‘Final Report on the Safety Assessment of Oleic Acid, Lauric Acid, Palmitic Acid, Myristic Acid, and Stearic Acid, International Journal of Toxicology.