I'm a little late to the (garden!) party, but we fight poison ivy every year as we live on a lake.
Just to make it stop itching for awhile, run the hottest water you can stand over the p/i spot for a minute or two (use a hot rag on your face). It'll itch like crazy for a few minutes, then quit itching for a long time.
For topical relief, we like Benadryl gel or if it's really bad, the doctor can prescribe some cream with Triamcinolone (sp?). You can also take Benadryl or the equivalent no-name allergy pills to dry the ivy up faster, plus reduce itching.
If things are really, really bad, either the doc or the ER can give you a shot or prescribe a round of steroids. Yes, we've had to do all of these things at one time or another. Hate that evil weed...I hope you get some relief soon! Liz