Why do snakes shed their skin?

A snake’s outer layer of skin is made of keratin and does not stretch as the animal grows, so it must be replaced. The process, called ecdysis, begins when a new layer forms underneath and a fluid separates the old skin. During this time the eyes turn cloudy blue because the scale covering each eye, the spectacle, is also being replaced, and the snake can barely see. The snake then rubs its snout against rough surfaces and crawls out, often leaving the skin inside out in one piece. Young, fast-growing snakes may shed every few weeks, while adults shed a few times a year.