The invention relates to a cosmetic agent in the form of a gel that contains undissolved, water-swelled polymer particles, and that reversibly forms a rough, uneven, refractive surface on the interface to gaseous substances while reversibly forming a smooth, even, non-refractive surface on the interface to solid substances. The preferred gelling agents are super-absorbent polymers. A preferred use of the inventive cosmetic agent is as an end protector when perming hair.