What Is It?
The Stearate salts, including Lithium Stearate, Aluminum Distearate, Aluminum Stearate, Aluminum Tristearate, Ammonium Stearate, Calcium Stearate, Magnesium Stearate, Potassium Stearate, Sodium Stearate, and Zinc Stearate are fine, white powders with a slight fatty odor. In cosmetics and personal care products, Stearate salts are used mainly in the formulation of makeup products such as eyeliner, eyeshadow, mascara, lipsticks, blushers, face powders and foundations. They are also used in fragrances, deodorants, and hair and skin care products.
Why is it used in cosmetics and personal care products?
The Stearate salts are generally used for their lubricating properties. They also help to keep emulsions from separating into their oil and liquid components. The Stearate salts increase the thickness of the lipid (oil) portion of cosmetics and personal care products and reduce the clear or transparent appearance of finished products.
The commercial stearic acid from which the Stearate salts are manufactured is actually a mixture of monocarboxylic acids obtained from animal and/or vegetable sources.
The Food and Drug Administration (FDA) includes Magnesium and Zinc Stearate on its list of substances considered Generally Recognized As Safe (GRAS) for direct addition to food. Salts of fatty acids (Aluminum, Calcium, Potassium and Sodium Stearate) are also permitted for direct addition to food. The FDA has also approved suitable grades of fatty acids and their aluminum, ammonium, calcium, magnesium, potassium, sodium, and zinc salts as indirect food additives. The safety of the Stearate salts has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. The CIR Expert Panel evaluated the scientific data and concluded that Lithium Stearate, Aluminum Distearate, Aluminum Stearate, Aluminum Tristearate, Ammonium Stearate, Calcium Stearate, Magnesium Stearate, Potassium Stearate, Sodium Stearate and Zinc Stearate were safe for use in cosmetics and personal care products. In 2001, as part of the scheduled re-evaluation of ingredients, the CIR Expert Panel considered available new data on the Stearate compounds and reaffirmed the above conclusion.
More safety Information:
CIR Safety Review: The CIR Expert Panel reviewed acute oral studies indicating that the Stearate salts were practically nontoxic, and had a low potential for acute dermal toxicity. Skin irritation studies demonstrated that Stearates were only minimal to slight irritants at high concentrations. Pharmaceutical vehicles containing 5.5% Magnesium Stearate were neither teratogenic nor mutagenic. Seven out of 20 human volunteers exhibited minimal to mild skin erythema when tested with an aqueous solution of 1.5% Ammonium Stearate.
Similar results were obtained with Sodium Stearate at 0.5%. In a 21-day patch test with 10 subjects, an aqueous formulation containing 0.1-0.25% Sodium Stearate caused minimal skin irritation. No sensitization was reported in 100 subjects tested with the same formulation. The CIR Expert Panel concluded that on the basis of the available information presented in the report that the Stearate salts were safe as cosmetic ingredients.
Link to FDA Code of Federal Regulations for the Stearate salts
Lithium Stearate, Ammonium Stearate, Potassium Stearate and Sodium Stearate may be used in cosmetics and personal care products marketed in Europe according to the general provisions of the Cosmetics Directive of the European Union. Aluminum, Calcium, Magnesium, and Zinc Stearates may be used as coloring agents in all cosmetics and personal care products (see Annex IV). If the stearic acid use to make these ingredients is derived from animal sources, it must comply with European Union animal by-products regulations.
More Scientific Information:
The commercial grade of stearic acid used to produce the Stearate salts contains fatty acids that range from 12 carbon atoms (C12, lauric) to C22 (behenic) and the major components are C18 (stearic) and C16 (palmitic) acids. In cosmetics and personal care products, the Stearate salts are used as emulsion stabilizers, viscosity increasing agents (nonaqueous), and opacifying agents. The water-insoluble metallic stearates are also water repellant and adhesive and have good “covering” properties.