Fumed silica is an amorphous silica product obtained by high-temperature hydrolysis of organohalosilane in a hydrogen-oxygen flame. Its primary particle size is between 7 and 40 nanometers, and its specific surface area is generally greater than 100m2/g. Very high, the silica content is not less than 99.8%. Fumed silica has been industrially produced since the 1940s. In the past few decades of industrial production, no cases of silicosis caused by inhalation of fumed silica have been found. The International Association for Research on Cancer (IARC) stated that there is currently insufficient evidence to prove that synthetic amorphous silica is carcinogenic to humans or experimental animals. On the contrary, IARC has listed crystalline silica as a carcinogen. In addition, the European Union The directive document (67/548/EEC) also states that amorphous silica is not a dangerous substance. Due to its good stability, physiological inertness, thickening properties, etc., it can be widely used in the field of daily necessities.

Fumed silica is a very important and very effective additive in body care products, and adding a small amount can have a significant effect. Since there are many hydroxyl groups on the surface of fumed silica, the interaction between particles is relatively strong. In the liquid system, the highly dispersed fumed silica easily interacts in the system to form a three-dimensional network, which makes the viscosity of the system. Increase, it can effectively prevent the flow of the system when it is at rest, and when an appropriate shear force is applied, the three-dimensional network is destroyed, making the system have a liquid flow shape, and when the shear force is removed, the network can be re-formed , so that the system can form a "gel" again. Therefore, it can play thixotropic and thickening functions in gel-like or paste-like products such as toothpaste, sunscreen, facial mask, etc. The dosage is generally 1-3%, and some are as high as 4-8%. For example, in pearlescent nail polish or spray-type care products, fumed silica mainly plays a role in suspension, so that various components in it are evenly dispersed in the system, preventing sedimentation and increasing the storage stability of the system. In hair care products, fumed silica also has a wide range of applications. For example, anti-dandruff shampoos contain some active ingredients such as selenium sulfide, salicylic acid, sulfur, zinc compounds, etc. Most of these ingredients need to be well dispersed and suspended in the system, which can be satisfied by adding fumed silica Require. Water-in-oil products generally have a greasy feeling. Adding fumed silica can reduce the greasy and sticky feeling. In oil-in-water products, fumed silica can improve the temperature and pH stability of the product. In sunscreen oil, adding surface-treated fumed silica can not only improve the texture, but also improve its water resistance, and the general dosage is 0.5-3%. Surface-treated fumed silica can improve the moisture resistance of pastes and gels, which is very beneficial for lipsticks, eyebrow oils, cosmetics, as well as whitening creams and sunscreens.