Proteins

Proteins are added to some personal care products for a variety of reasons. They can act as emulsifiers ant-static agents, film formers, thickners, and humectants but they have no biological significance. 

Contrary to advertisers' claims, proteins cannot be absorbed by hair, skin, or nails and they cannot repair or improve our body tissues. To imagine that these proteins can do what the marketing people suggest is just as ludicrous as trying to repair a crumbling house by throwing bricks and sand at it.

Reference: Cosmetics Unmasked: Dr. Stephen & Gina Antczak