Final answer:
A topical corticosteroid cream, such as hydrocortisone, is used to treat contact dermatitis, poison ivy, insect bites, and psoriasis by reducing inflammation and relieving symptoms like itching and rashes.
Step-by-step explanation:
A topical agent commonly used to treat contact dermatitis, poison ivy, insect bites, and psoriasis is a corticosteroid cream. One example is hydrocortisone cream, which contains a synthetic form of cortisol, a hormone produced in the adrenal glands. When applied directly to the skin, hydrocortisone reduces inflammation, itching, and rashes by suppressing the immune system and reducing the secretion of histamine, a compound involved in the inflammatory response.