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Medically reviewed by: Amy W. Anzilotti, MD

What Is a Cast?

A cast is a hard bandage that keeps part of the body from moving so it can heal

Why Do Kids Need Casts?

Kids 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 can be molded to the body part. It dries hard. Some fiberglass casts are waterproof. Doctors only use this type of cast for some kinds of broken bones.

Another type of cast is made of plaster of paris. This white powder is mixed with water into a paste. The paste hardens when it's dried.

How Are Casts Put On?

To put on the cast, a 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 covering

A fiberglass cast gets warm as it hardens. It cools in about 15 minutes.

How Can We 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.


  • 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.
  • Have a parent help you use a hair dryer on the cool or fan-only setting to blow air in at the edges of the cast.
  • Never use an anything like a pencil or hanger to scratch under the cast. Scratching can lead to an infection. Don't put lotion or powder inside the cast.

How Should We Care for the Cast?

If the Cast Is Waterproof Have a Parent Help You:

  • Flush the cast and liner with clean water to remove soap after showers. 
  • Dry the waterproof cast with a hair dryer on cool 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, have a parent help you 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 or online.
  • Keep the cast out of the water by propping it up on the side of the tub. 

If the cast or liner gets splashed, have a parent help you 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.

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.

When Should We Call the Doctor?

Your parent should call the doctor if:

  • The cast feels too tight.
  • The cast was comfortable but now is 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, such as a piece of food or small toy. 
  • A bad smell or any kind of fluid is coming from the cast. 
  • A non-waterproof cast or liner gets wet.

What Else Should I Know?

Take care of your cast so it stays in good condition. Sometimes your doctor will let you keep your cast as a souvenir — all you have to do is ask. You can look at it in the future, read what your friends wrote on it, and remember how you got better!

  • Taking Care of a Cast

    Taking Care of a Cast

    Casts help protect broken bones while they are healing. Find out how to care for a cast.

Medically reviewed by: Amy W. Anzilotti, MD
Date reviewed: March 2023