Broken bones usually take about six to eight weeks to heal, according to Health First. While your broken arm is healing, it will be immobilised in a cast that is typically made from plaster and fibreglass. If the cast becomes dirty or wet (due to either water or body sweat), it may start to smell. If the smell of your cast is intense, see your doctor before you try to clean it. The bad smell may indicate that the skin underneath the cast is infected.
Wipe the arm cast with a dry cloth to remove loose dirt.
Dampen the cloth slightly if a dry cloth is not sufficient to remove the dirt or smudges. Wring the cloth after dampening. Do not allow any excess water to drip on the cast. Wipe the smudges lightly.
Keep the dampened area of the cast in open air until it is completely dry. According to Health First, you may accelerate the drying by using a hair dryer on the cast. Only set the dryer to the cool setting to avoid burning yourself and hold it several inches away from your arm.
Rub a pinch of baking soda into any areas that appear soiled to prevent odours.
Avoid placing any objects, such as a coat hanger, underneath the arm cast to scratch your skin. The object is not likely to be sterilised, so it may dirty the cast. Health First points out that it may also break the skin on your arm, which can lead to an infection.