Health Library

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 breaking a bone, other injuries, and some surgeries.

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.

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 (waterproof casts get a different liner)
• 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 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.
• 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 We 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 setting after showering or swimming.

If the Cast Is Not Waterproof:

Casts that don’t have a special waterproof liner must stay dry. Even kids who are old enough to bathe alone will need help to keep the cast dry while bathing.

• Younger kids should get sponge baths. To give a sponge bath, use a wet sponge or washcloth to wash and rinse your child. Do not put him or her into the water.
• Older kids can take baths. Baths are better than showers because it is easier to keep the cast dry in a bath.
  • 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 families use a waterproof plastic cast protector instead of plastic bags. You can buy this at a drugstore or online.
  • 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.

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 I Call the Doctor?

Call your doctor if:

• The cast feels too tight.
• The cast was comfortable but becomes uncomfortable.
• Your child has new pain or pain that gets worse.
• The 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?

Casts can be inconvenient, but most kids don’t have any problems with them. Help your child take care of the cast so it stays in good condition and doesn’t cause irritation. Within a few months, most kids can get back to all the activities they enjoy.