Moisturizing cosmetic forms - Evaluation of skin hydration

Cosmetic forms and technologies

The moisturizing effectiveness of a formulation is not only linked to the presence of specifically moisturizing ingredients, but also the choice of the vehicle and the cosmetic form that contributes to the conferment of this property. Since lipid emollients are the main components of cosmetic treatments for dry and dehydrated skin, among the most widely used cosmetic forms, in addition to oil emulsions in water with a high fat phase content, we can find emulsions with an external oily phase (A / O ), more occlusive and persistent on the skin than the previous ones, or anhydrous systems, obtained by mixing different types of oils. On the market there are also spray oils, generally formulated on a silicon base to reduce the stickiness and greasiness of the finished product, with a high content of liposoluble active ingredients, such as vitamin E. Good response, due to its ease of application compared to oleolites, finally find the lipogels, mixtures of fluid oils viscosized with a gelling agent and suitably functionalized. Microemulsions represent an innovative release system of cosmetic ingredients with numerous advantages compared to the more traditional formulas.1 Able to solubilize both lipophilic and hydrophilic ingredients capable of interacting more effectively with skin constituents. In the case of microemulsions, the formulas are capable of delivering greater hydration.

Evaluation of skin water content

There are several systems with which it is possible to evaluate and measure the skin's water status. The most widespread and used method is the corneometric method that allows to obtain an indirect measure of the water content of the stratum corneum, through the determination of its capacitative properties.

The corneometer is a low frequency capacitance meter, able to appreciate the water content present in the epidermis at a depth of about 60-100 μm. A sheet of conductive material is electrically charged and takes on, together with the epidermal surface, the functions of a capacitor. A microprocessor calculates the capacitance of the system. The measured values ​​are a function of the resistivity of the stratum corneum, which in turn depends on the concentration of water within the corneum itself.

A different device, the Novameter, uses frequency currents up to 1 Mhz, but the water content is measured at a more superficial level.

With the use of the Tewameter it is possible to evaluate the TEWL and thus determine the efficiency of the barrier function. Decreasing the TEWL means being able to conserve water inside the epidermis, reducing the amount lost with perspiratio insensibilis.