If you need a cast for a broken arm, to mend after knee surgery, or for another injury, you may wear it for several weeks or months. The cast keeps your bone or joint from moving so it can heal. But it also can cause discomfort and problems, from an annoying itch to a serious infection.
Types of Casts
You’ll likely get one of two main kinds of casts. Both are hard, and both go on top of a layer of cotton or other soft padding that rests on your skin.
Plaster cast. This is made of plaster of Paris, a white powder that, when mixed with water, turns into a thick paste that hardens. Take care not to get your cast wet. It can start to dissolve or irritate your skin. Take baths instead of showers. Cover the cast with a plastic bag or a sleeve sold in drugstores. If it gets wet, dry it with a blow-dryer on a cool setting, or suck air through the cast with a vacuum cleaner hose.
Fiberglass cast. Also called a synthetic cast, it's made of fiberglass, which is a type of plastic that can be shaped. It’s lighter and more durable and expensive than plaster casts. X-rays also “see” through it better. Fiberglass is water-resistant. But the padding underneath is not, so it’s best to keep it away from water.
If you don’t have a fracture, your doctor may recommend a cast made of elastic or other soft material. It can be removed without a cast saw and could be a good choice for young children or someone who’s had surgery.
Your cast may feel snug, especially the first few days after your injury. Usually it’s from your body swelling. To make it go down:
- Prop up the injured part of the body so it’s higher than your heart. If the cast is on your leg, lie down and put cushions or pillows underneath. This helps drain blood and fluids away from the injured area.
- Wiggle your fingers or toes on the injured arm or leg, and do it often. This also can prevent stiffness.
- Chill the cast from the outside with a plastic bag of ice, or an ice pack wrapped in a thin towel. Keep the ice on the cast at the site of the injury for 15-30 minutes. Repeat every few hours for the first few days. Be sure to keep the cast dry.
- If you feel sore or swollen, ask your doctors if you should take over-the-counter pain meds like acetaminophen or ibuprofen.
It can be maddening if you can’t reach a spot you need to scratch. Locate your itch, and tap it on the outside of the cast. You can also try blowing cool air from a hair dryer around the edges of the cast. Don’t give into temptation and stick a pencil, a ruler, or any other objects inside the cast to relieve the itch. That could break your skin. Avoid applying lotions, oils, deodorant, or powder in or around the cast.
It’s normal for your cast to get smelly after you’ve worn it for a while. But if you notice a foul odor or a discharge coming from the cast, it could mean your skin underneath is infected. Get it treated right away.
When to Call Your Doctor
You also should alert your doctor if you have:
- A fever (higher than 100 F for child and 101 F for adult)
- Numbness, tingling, burning, or stinging in the injured arm or leg
- Sores under the cast
- Pain or swelling that gets worse
- Cold, pale, or bluish skin
- A crack or soft spots in the cast
- Wet cast that won’t dry
- A cast that’s too tight or too loose
- Red or raw skin around the cast
- Trouble moving fingers or toes