Sausage casings are the material that encloses the filling of a sausage. There are three types of sausage casings: natural, artificial, and synthetic.

• Natural casings are made from animal intestines or skin. In Western European cuisine and Chinese cuisine, most casings come from pigs, but elsewhere the intestines of sheep, goats, cattle, and sometimes horses are also used. Natural casings are made from the sub-mucosa of the small intestine of meat animals, a layer of the intestine that consists mainly of naturally occurring collagen. To prepare the intestines as casings, they are flushed, scraped, and cleaned with water and salt by hand or with machinery.

• Artificial casings are made of collagen and cellulose. Collagen casings have been around the longest and are produced from animal collagen, mostly from the hides of cows and pigs. Sometimes the bones and tendons are included, and the casings can also be made from poultry and fish. Collagen casings are less expensive to use, give better weight and size control, and are easier to run when compared to natural casings. The latest generation of collagen casings are usually more tender than natural casings and do not exhibit the "snap" or "bite" of natural casing sausages. Most collagen casings are edible, but a special form of thicker collagen casings is used for salamis and large caliber sausages where the casing is usually peeled off the sausage by the consumer.

• Synthetic casings are made of materials such as cellulose, plastic, and other polymers. They are not edible and are used for sausages that are not cooked, such as salami and summer sausage.

In summary, natural casings are made from animal intestines or skin, artificial casings are made of collagen and cellulose, and synthetic casings are made of materials such as cellulose and plastic.