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Why do snakes and lizards shed their old outer skin in sheets or pieces?

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A pangolin walks through grass with a blue circle around it and the word endangered written in white across the image. — Integument The pangolin is the only mammal in the world covered in scales.

Snakes and lizards shed their outer skin, a process known as ecdysis or molting, primarily because their skin does not grow along with their bodies. As these reptiles increase in size, they must periodically replace their old, restrictive outer layer with a new, functional one.123

The shedding process is essential for maintaining the animal's health and hygiene. It allows them to remove parasites, such as mites, that may have attached to the old skin. Additionally, the skin acts as a primary buffer against environmental damage, and shedding ensures the animal maintains a fresh, protective layer.143

While the biological purpose is the same, the method of removal differs between the two groups:
* Snakes typically shed their old skin in a single, complete sheet.25
* Lizards generally shed their skin in patches or smaller pieces.25

In both groups, the germinal layer of the epidermis forms a complete new skin surface beneath the old one before the process of sloughing begins. This cycle is hormonally controlled and influenced by factors such as age, physical condition, and environmental conditions like temperature and humidity.52