Are there any risks associated with the cosmetic use of silica?

The introduction of silica nanoparticles in certain cosmetic formulations (particles <100 nm) has prompted increased scrutiny from regulatory authorities. The SCCS recommends a case-by-case assessment focusing on structure, surface, solubility, and bioavailability. Available data suggest that cutaneous penetration of nanoscale silica is very low to nonexistent on intact skin. However, if the skin barrier is compromised, permeability could theoretically increase. European regulations require that silica nanoparticles be surface-modified, insoluble and not present in products intended for inhalation, such as sprays or aerosols. To date, no systemic toxic effects have been demonstrated in vivo under normal cosmetic use conditions.

The primary risk associated with cosmetic silica involves theinhalation of particles, particularly in loose powders (foundation powders, finishing powders) or spray products. Even in its amorphous form, silica in suspension can cause upper respiratory tract irritation after prolonged or repeated exposure. This risk is increased if the particle size is below 10 µm, allowing them to reach the pulmonary alveoli.

Inhalation of fine particles of silica, present in certain cosmetic products in the amorphous or crystalline, can lead to pulmonary inflammatory reactions and health risks. Studies show that the toxicity of silica depends on the surface structure of the particles. Among these surface features, the 'quasi-free' silanol groups play an important role. These small chemical moieties (≡Si–OH) are sufficiently accessible to interact strongly with human cell membranes, such as those of the lungs. These interactions can damage cells and trigger an inflammatory response from the immune system. If this inflammation persists due to repeated or prolonged exposures (for instance, among workers exposed to crystalline silica dust), it can lead to chronic diseases such as silicosis as well as autoimmune disorders.

The skin tolerance of amorphous silica is generally good. In vitro and in vivo studies confirm the absence of irritation, sensitization or cutaneous toxicity. Its mode of action relies solely on physical properties, such as the absorption of sebum, formula texture modification and optical light diffusion. Sensations of dryness or transient discomfort may, however, occur on dry or sensitive skin due to its absorption capacity. When used in a granular (non-spherical) form, silica can also serve as a mechanical mechanical exfoliating agent. In this case, the choice of particle size is crucial to prevent excessive abrasion.

From an environmental standpoint, silica has a favorable profile. Unlike the microplastics formerly used as exfoliants (polyethylene, nylon), silica is mineral, non-persistent in aquatic environments, and non-bioaccumulative. It thus represents a sustainable alternative in rinse-off products and eco-friendly formulations.

From an environmental standpoint, silica is a more environmentally friendly option. Unlike microplastics such as polyethylene or nylon, formerly used in scrubs, silica is of mineral origin, meaning it is primarily derived from sand or quartz. It does not linger in water, does not cause lasting pollution in rivers or oceans, and does not accumulate in living organisms. This is why it is considered a greener alternative, particularly in rinse-off products or in treatments designed to minimize their environmental impact.