Why use an opacifier in cosmetics?

An opacifier is a cosmetic ingredient used to give a creamy and rich appearance to a formulation. This could be pearlescent waxes, latex copolymers or dyes for example. As their name suggests, opacifiers make products more opaque, meaning they partially or completely block the transmission of light through the formulation. This opacity can give the product a white or denser look, thus altering its appearance to meet consumer expectations. In addition to their aesthetic role, opacifiers can also perform more technical functions.

• Some opacifiers contribute to stabilising formulas : The use of certain opacifiers, such as paraffin or cetearyl alcohol, can help to enhance the stability of skincare products. These ingredients can act both as opacifiers and as emulsion stabilisers: they thus assist the surfactants by limiting the separation of the oil and water phases, which helps to extend the product's shelf life.

• Some opacifiers can counteract UV rays : Certain opacifiers, such as titanium dioxide, have the ability to absorb or reflect UV rays and offer additional protection against light-induced damage, both for the cosmetic product and the consumer themselves. These opacifiers are particularly useful when formulas incorporate photosensitive ingredients, like Vitamin C.

• Opacifiers can assist in controlling the consistency of products : The addition of an opacifier also allows for the adjustment of the product's consistency, thus complementing the action of the texturing agents. By giving the treatments a more or less milky consistency, opacifiers influence the sensory experience of consumers.

In cosmetics, there are numerous different opacifiers, each offering varied benefits. Here are a few:

• The titanium dioxide.

  Titanium dioxide is one of the most commonly used opacifiers in cosmetics. Also used as a UV filter, it has significant opacifying properties, allowing it to give products an opaque white appearance. Titanium dioxide nanoparticles sometimes raise concerns as they are suspected to be carcinogenic and capable of penetrating the skin barrier. However, when used as an opacifier, titanium dioxide is present in microscopic form: it is then too large to pass through the stratum corneum and is not considered concerning.

• The zinc oxide.

  Just like titanium dioxide, zinc oxide is used in microscopic form for its opacifying properties and is capable of filtering UV rays. It should be noted that zinc oxide nanoparticles, which are the subject of various controversies, are not used as opacifiers because their small size negates their whitening effect.

• The magnesium stearate.

  Magnesium stearate is a derivative of stearic acid, a fatty acid, commonly used for its opacifying properties and its ability to control the texture of the product. It is frequently found in compact powders and lipsticks.

• The waxes.

  Natural waxes, such as beeswax, candelilla wax, or carnauba wax, also play a significant role in the opacification of cosmetics. In addition to providing a more solid or creamy texture to formulations, they offer a matte and rich finish. Waxes are also valued for their emollient properties, allowing them to soften the skin.

• The mica.

  Mica is another opacifying agent typically used to alter the consistency of creams and soaps. This mineral is obtained via the extraction of raw rock and can bring colour to makeup products, such as lipsticks and eyeshadows. Mica allows for different finishes: satin, pearlescent, shiny reflections...

• Talc.

  In addition to possessing mattifying properties, talc can reduce the transparency and translucency of cosmetics, hence it is often used as an opacifier. However, it is important to note that this compound has been flagged for several years for its harmful health effects. In 2024, talc was classified as "probably carcinogenic to humans" (Group 2A) based on a combination of "limited" evidence of cancer in humans, "sufficient" evidence of cancer in animals, and "strong" mechanistic evidence in vitro.

• DRAELOS Z. K. Cosmetics: An overview. Current Problems in Dermatology (1995).

• FERRITO S. & al. Polymers for Personal Care and Cosmetics: Overview. ACS Symposium Series (2013).

• BAKI G. Introduction to Cosmetic Formulation and Technology. Wiley (2023).

• STEWART P. & al. Carcinogenicity of talc and acrylonitrile. The Lancet Oncology (2024).