A patient with a fractured arm is receiving a plaster cast for immobilization of the left arm. The provider is giving discharge instructions to the patient on proper cast care. Which instruction should the provider prioritize?

Applying powder or lotion under the cast can lead to moisture retention, which increases the risk of skin irritation and infection. It is generally advised to avoid putting anything inside the cast, as this can also disrupt the healing process and compromise the cast's effectiveness.

Cutting or modifying the cast without professional guidance can lead to improper support for the fracture, potentially hindering recovery. Patients should always consult their healthcare provider if they experience discomfort or irritation rather than attempting to adjust the cast themselves.

Using objects like a pencil to scratch an itch inside the cast is highly discouraged as it poses a risk of injury to the skin and could lead to infection. The cast should remain intact to provide proper immobilization, and itching can often be managed through other methods, such as gently tapping the cast or using a cool air blow.