The primary function of a purifying mask is to absorb excess sebum in order to reduce shiny areas and imperfections. Therefore, certain components are essential in the composition of a purifying mask, notably absorbent active ingredients such as charcoal or clay, which are compounds porous enough to absorb excess sebum. These masks also include emollients, often vegetable oils, which soften and make the skin more supple to prevent it from drying out.
Typically, purifying masks have a consistent, gel-like texture. This characteristic is imparted to the product through texturising or gelling agents which are most often polymers (ex : xanthan gum, sclerotium gum, etc.). They have the property of giving the product consistency by increasing its viscosity. There are also pH regulators (ex : calcium carbonate, etc.) to stabilise the preparation and adjust the pH of the mask to that of the skin.
A purifying mask also contains humectant compounds (pentylene glycol, glycerine, etc). The humectant nature of an ingredient is based on its ability to retain water molecules due to its hygroscopic power. These compounds help to maintain the fluidity of the mask.
Furthermore, a purifying mask is composed of an aqueous phase (water, hydrosol) which can be conducive to the growth of bacteria. In response to this, to maintain the effectiveness and safety of the product, it is essential to incorporate preservatives (sodium dehydroacetate, sodium benzoate, etc.) that will ensure the stability of the mask over time.