Magnesium aluminum silicate is a complex silicate refined from naturally occurring minerals. It is used in a variety of cosmetics and personal care products as a viscosity-increasing agent, absorbent, anticaking agent, opacifying agent, and emulsion stabilizer.
Magnesium aluminum silicate is a naturally occurring mineral derived from silicate ores of smectite clay. It is refined to a powdery, dry-feeling, white solid for use in cosmetics and pharmaceutical applications. Due to the large size of its molecules, magnesium aluminum silicate is unable to be absorbed into the skin. Magnesium aluminum silicate is often used in products that have a high pH level, such as depilatory, waving, and hair relaxer products.
In cosmetics and personal care products, magnesium aluminum silicate functions as a viscosity-increasing agent, absorbent, anticaking agent, opacifying agent, and emulsion stabilizer.
A primary function of magnesium aluminum silicate is as a viscosity-increasing agent. The term viscosity corresponds to the concept of “thickness”, for example, honey has a higher viscosity than water. Therefore, as a viscosity-increasing agent, magnesium aluminum silicate works to thicken formulations in order to make a product less runny and easier to spread. This property is especially useful in deodorants, shaving creams, and thick lotions. Additionally, magnesium aluminum silicate acts synergistically with other common thickeners like xanthan gum and HE cellulose.
Magnesium aluminum silicate is classified as an absorbent because it has the ability to absorb or soak up liquids. Due to this property, magnesium aluminum silicate can also be used as an anticaking agent. By absorbing liquids, it prevents powder products from clumping together (caking) and helps other ingredients to apply more smoothly. Furthermore, as an opacifying agent, magnesium aluminum silicate can be added to clear or transparent cosmetic formulations to render them more resistant to visible light.
Lastly, magnesium aluminum silicate functions as an emulsion stabilizer. An emulsion is a mixture of two or more immiscible liquids, for instance, water and oil. Mixing water and oil together creates a dispersion of oil droplets in water (and vice versa). However, these two phases can separate if the product is left to settle. The smectite colloidal structure of magnesium aluminum silicate effectively keeps the internal phase droplets suspended and separated and reduces the tendency of emulsions to thin out and break at elevated temperatures. Magnesium aluminum silicate can stabilize both oil-in-water and water-in-oil emulsions at low concentrations (typically at 1 to 2%).
The safety of magnesium aluminum silicate has been assessed by the Cosmetic Ingredient Review (CIR) Expert Panel. Because of its solid particle form, some studies have shown that this ingredient could be irritating if contact is made with the eyes. Topical application of magnesium aluminum silicate to human skin daily for one week produced no adverse effects. It was not found to be irritating or sensitizing to the skin. Since magnesium aluminum silicate is made up of large particles, this ingredient cannot be absorbed by the skin. Therefore, it cannot cause sensitization reactions because it cannot react with cells of the immune system. After evaluating the scientific data, the CIR Expert Panel concluded that magnesium aluminum silicate was safe as used in cosmetics and personal care products.
According to EWG’s Skin Deep Cosmetic Database, magnesium aluminum silicate is considered to be safe as used in cosmetics and personal care products. It is rated as a 1 on a scale of 1 to 10, with 1 being the lowest risk to health and 10 being the highest.
References: Making Cosmetics “Magnesium Aluminum Silicate”, Cosmetics Info “Magnesium Aluminum Silicate”, Int J Toxicol. 2003;22 Suppl 1:37-102.