Final answer:
The cream prescribed for treating a rash on the forearm should be administered topically. Corticosteroid creams, like hydrocortisone, reduce inflammation and relieve symptoms, but they don't necessarily address the underlying cause of the rash.
Step-by-step explanation:
The correct administration of the cream prescribed for a rash on the forearm would be topically. This means it should be applied directly to the surface of the skin, where the rash is located. In reference to corticosteroid creams, such as one containing hydrocortisone, they work by reducing inflammation and relieving symptoms such as itching and rashes by suppressing the local production of histamine in the skin. However, these creams may not treat the underlying cause of the rash, which is evident in cases like Penny's, where the rash worsened, indicating the need for further medical evaluation.