Calamine is very good for poison ivy and any other itch that comes with an infection. Calamine has about 0.5 % Zink oxyde. Zink oxyde is a great anty-irritant and desinfectant.
With bad bites, I apply first Solar Cayne, which is an anesthetic with aloe, and then I apply calamine. I also keep Zink oxyde and triple antibiotic cream in my first aids box.