What Is a Cast? A cast is a hard bandage that keeps part of the body from moving so it can heal. Why Do People Need Casts? People get casts after a broken bone, some surgeries, and other injuries. What Are the Different Kinds of Casts? Most casts are made of fiberglass. Fiberglass is a kind of plastic that is moldable and dries hard. Some fiberglass casts are waterproof. Less often, casts are made of plaster of paris. This white powder is mixed with water into a paste. The paste hardens when it's dried. Is There a Waterproof Cast? Yes, there is a cast that can be worn in showers and pools. A waterproof cast is a regular fiberglass cast with a different type of liner. Doctors use waterproof casts only for some kinds of broken bones. How Are Casts Put On? A health care provider such as an orthopedic surgeon , emergency room doctor, physician assistant , orthopedic technician, or nurse practitioner puts on the cast. To put on the cast, the health care provider: wraps a liner of soft material around the injured area (for a waterproof cast, a different liner is used) wets the cast material with water wraps the cast material around the first layer waits until the outer layer dries to a hard, protective covering A fiberglass cast gets warm as it hardens. It cools in about 15 minutes. How Can I Prevent Problems With a Cast? If the cast is not waterproof, keep the cast and liner dry. A wet cast or liner can lead to a skin rash or infection. Also: Don't pull out the lining or break off any parts of the cast. If there is a sharp edge, put tape or moleskin on the edge of the cast. If the cast is itchy: Tap on the outside of the cast. Use a hair dryer on the cool or fan-only setting to blow air in at the edges of the cast. Never use an object to scratch under the cast. Scratching can lead to an infection or sores. Don't apply lotion or powder inside the cast. How Should I Care for the Cast? If the Cast Is Waterproof: Flush the cast and liner with clean water to remove soap after showers. Dry the waterproof cast with a hair dryer on the cool or fan-only setting after showering or swimming. If the Cast Is Not Waterproof: Casts that don't have a special waterproof liner must be kept dry. It is better to take a bath than a shower because it is easier to keep the cast dry in a bath. To keep the cast dry while bathing: Before the bath, cover the cast with two plastic bags. First, put one bag on and seal the top with a rubber band. Then, put the second bag on and seal it with another rubber band. Some people use a waterproof plastic cast protector instead of plastic bags. You can buy this at a drugstore. Keep the cast completely out of the water by propping it up on the side of the tub. If the cast or liner gets splashed, gently blow air into it from a hair dryer on the cool or fan-only setting. If some of the cast or liner goes under water or gets very wet, call your doctor. When Should I Call the Doctor? Call your doctor if: The cast feels too tight. The cast was comfortable but is now uncomfortable. You have new pain or pain that gets worse. Your fingers or toes get more swollen, change colors, hurt, or feel numb. Something is stuck in the cast, like a piece of food. A bad smell or any kind of fluid is coming from the cast. A non-waterproof cast or liner gets wet. How Are Casts Taken Off? Health care providers take off casts with a small electrical saw. The saw cuts through the cast material but stops before it touches the skin. When the cast is off, the skin will probably look pale, dry, or flaky. The hair will look darker and the muscles will look smaller. This is normal and goes away within a few weeks. Looking Ahead Take care of your cast so it stays in good condition and does not lead to irritation. Within a few months, you can get back to all the activities you enjoyed before the injury. 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Read More Bones, Muscles, and Joints Our bones, muscles, and joints form our musculoskeletal system and enable us to do everyday physical activities. Read More Sports and Exercise Safety Playing hard doesn't have to mean getting hurt. The best way to ensure a long and injury-free athletic career is to play it safe from the start. Find out how. Read More Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.