I am very susceptible to poison ivy, especially in the warm months when I am fishing and clambering around riverbanks.
Two products - a cleanser called Tecnu and a laundry bar soap called Fels-Naptha - are crucial to me for an ivy-free summer.
The Tecnu stuff (get at any chain drugstore) should be applied as soon as possible after you suspect you've been exposed. It lifts the oils out instead of just covering them up like that nasty pink stuff. Scrub vigorously and rinse, then repeat.
I use the Fels-Naptha soap in the shower later. Keep it out of your eyes, whatever else you do. You might feel somewhat abraded afterwards, but it beats the alternative.
Finally, wash anything you were wearing separately from anything else and do it promptly.
And if you don't know what poison ivy and its even nastier cousin poison sumac look like, get a field guide and find out. It's always better not to get in it in the first place.
I hope these tips from a fellow sufferer are useful.