Stearic Acid in Cosmetics and Personal Care Products

Stearic acid is one of several long-chain fatty acids that appears as a white, waxy, solid substance, often crystalline in structure. It’s used as a surfactant and softening agent in cosmetics and as an emulsifier and thickening agent in detergents and soaps.

What is Stearic Acid?

Stearic acid is a saturated fatty acid with an 18-carbon chain. Its IUPAC name is octadecanoic acid and its formula is CH3(CH2)16CO2H. It is present in animal fats and oils and in some kinds of vegetable oils in the form of glycerides. You can find stearic acid in plant fats such as shea butter and coconut oil. Stearic acid is mainly used for the production of stearates such as sodium stearate, magnesium stearate, calcium stearate, lead stearate, aluminum stearate, cadmium stearate, iron stearate, and potassium stearate.

Use of Stearic Acid in Cosmetics and Personal Care Products

Stearic acid is especially common in producing detergents, soaps, and cosmetics, such as shampoos and shaving cream products. Soaps are not made directly from stearic acid but indirectly by saponification of triglycerides consisting of stearic acid esters.

One of the reasons stearic acid is so desirable in cosmetics is its bifunctional character – it has a polar head group that can be attached to metal cations and a nonpolar chain that confers solubility in organic solvents. The combination is ideal for use as a surfactant and softening agent.

What does STEARIC ACID do in a formulation?

Emollient: Stearic acid is used as an emollient. Stearic acid helps lock in moisture by forming a protective barrier on the skin, preventing water loss and keeping the skin hydrated and supple.
Emulsifying agent and Emulsifying stabilizer: Stearic acid acts as an effective emulsifying agent allowing it to blend and stabilize oil and water-based ingredients in formulations. It helps to prevent separation and maintain the desired consistency of products
Thickening Agent: Due to its waxy nature, stearic acid can act as a thickening agent in various formulations.
Hair conditioning: It is an excellent conditioner for the hair, acting as a barrier against harmful environmental elements without weighing down the hair. Stearic acid also improves the texture of hair products and helps them spread more evenly.

What is STEARIC ACID used for?

Stearic acid is used to thicken the products and bind the ingredients together. It has moisturizing and anti-inflammatory properties that make this ingredient a very popular choice in cosmetic and skincare products.

Skin care
Hair care
Cosmetic products

Product Examples

Type	Examples
Skin Care	Face Creams, Moisturizing Lotions
Bath & Body Care	Foaming Body Wash, Body Cleanser
Hair Care	Hair Conditioners, Shampoos, Hair Masks, Styling Pomade
Deodorant	Deodorant Sticks

Stearic Acid Formulation Considerations

Stearic acid is incompatible with strong oxidizers and strong bases. Avoid using stearic acid in higher pH formulations such as hair colors.
Stearic acid is incompatible with reducing agents.
It is insoluble in water and hence it does not dissolve in water-based solutions. However, it can be soluble in organic solvents like ethanol and ether.
Stearic acid is odorless Stearic acid and makes it an ideal ingredient for products where fragrance or scent is not desired.

Health Effects of Stearic Acid

Stearic acid may cause allergic reactions in people with sensitive skin and is considered somewhat comedogenic.
Stearic acid is generally considered nontoxic. However, inhalation of dust irritates the nose and throat. Dust causes mild irritation of the eyes.
Stearic acid is combustible when exposed to heat or flame. To fight a fire, use CO2 and dry chemicals. When heated to decomposition, it emits acrid smoke and irritating fumes.
Stearic acid is a halal ingredient and safe for skin and hair when used in limited quantities. All skin types are appropriate for this ingredient. However, a patch test is recommended before usage.

Acceptable Limits or Maximum Usage

The maximum usage level of Stearic Acid in the Personal Care industry per the Cosmetic Ingredient Review regulatory agency is as follows:

Usage Level	Category
0.1-5%	Baby Lotions, Oils, Powders, and Creams
1-5%	Bath Preparations
1-10%	Eyeliner, Mascara, Eye shadow, and Eyebrow Pencil
1-5%	Perfumes, Cologne, and Toilet Waters
1-5%	Hair Conditioners and Hair Sprays
5-10%	Hair Shampoos and Hair Straighteners
4-10%	Shaving Creams and Shaving Soap
1-5%	Skin Cleansing Preparations (Cold Creams, Lotions, Liquids)