You should keep applying calamine lotion to the blisters as often as you can, I.e. Several times a day.
I have a patch of poison ivy or poison sumac in my yard and have tried unsuccessfully to pull it out. I pull it out each year and it keeps coming back. I got into this small patch about a week ago and still have the blisters to prove it. I put calamine lotion on my blisters many times a day to dry it up.
Oh, I would like to correct the misconception that poison ivy is not able to spread. I originally got the poison ivy on my left wrist (while pulling out the plant). I sleep on my left side with my left wrist touching my right shoulder. I now have 2 separate patches of blisters on my right shoulder where my left wrist rests when I sleep.
Also, if you scratch the blisters DO NOT touch your eyes or your face or you will spread the poison ivy onto your face and can actually get it in your eyes. A friend of mine had poison ivy in her eyes and had hell to pay until it got cleared up (very expensive treatment by the way). So, yes you can spread it not only to yourself but to other people who are sensitive to poison ivy. Also, wash your bedding more than usual and don't wear the same nightclothes 2 nights in a row.