We have bars of brown soap at every sink & shower. Fels Naptha is one brand. When we come in from gsrdening or being near poison ivy, we scrub with it. We also lather it onto the infected area & let it dry on the skin. When all finished you may need some lotion for dry skin, but it seems to work! Just getting over a nasty case!
For many years I was the one who never got poison ivy. When we moved here 35 yrs ago, I was pulling 2" & 3" vines out of locust trees & got it for the 1st time. I was told there are different strains, & once you get one you get all the others! Also, I have certain garden areas where there no longer is the ivy itself, but the oil remains in the soil for years. I now wear gloves!
Good luck!