What is the best treatment of poison ivy?

Anti itch. Hydrocortisone 1% available otc can be used to decrease the itch. Sometimes, a sedating anti histamine like Benadryl (diphenhydramine) can also make the itching less pronounced.
Poison ivy. There are specific products that you can buy that will wash the Urushiol off. Some options of treating poison ivy include calamine lotion, oatmeal soaks, hydrocortisone cream and antihistamines. Anything which has touched urushiol from the poison ivy needs to be cleaned (clothes, shoes, gear etc.) Oral steroids are sometimes indicated. .