A soft white clay that soaks up surface oil in masks and adds body to toothpaste. It works physically; it doesn't draw out toxins or shrink pores.
Kaolin is a fine, mild clay mineral. In face masks it absorbs sebum and dirt from the surface as it dries, leaving skin matte for a while; it is gentler and less drying than bentonite clay. In toothpastes and tabs it adds body and a mild polishing effect.
The effect is physical and temporary: oil returns within hours, and clay doesn't pull 'toxins' out of skin.
Its oil-absorbing capacity is a known physical property, but controlled trials of kaolin masks for acne or pore appearance are essentially absent.