Fibroin

Fibroin is obtained from the cocoons of the silkworm (Bombyx mori). Approximately 70–80% of silk fibers consist of fibroin, while the remaining portion is mainly composed of sericin. Prior to cosmetic use, fibroin is purified and processed into a suitable form for incorporation into formulations.

Fibroin and hydrolyzed silk protein are not exactly the same. Fibroin is the native silk protein, whereas hydrolyzed silk protein is produced by breaking fibroin down into smaller peptides. This hydrolyzed form is more water-soluble and can be more easily incorporated into cosmetic formulations.

Effects on the skin:

Forms a delicate protective film on the skin surface.
Helps reduce transepidermal water loss, thereby supporting the maintenance of skin hydration.