Cortisone ointment (the strongest you can find OTC) is your friend. Also, as soon as you get done gardening, shower using some Dr. Bronner's castille soap. Yeah, I know it dries your skin out, but it will cut the poison ivy oils.

My son gets it really badly every year. Last year, it covered about a quarter of his skin and it was scary. It took cortisone ointment, oatmeal baths, and a bit of benadryl to help that kid.

The more you're exposed to urushiol oil (the ingredient that makes poison ivy "poison"), the more sensitized you generally become. If you had a bad outbreak last year, you really need to take further exposures seriously, and not only wear protective gear, but get rid of it, if it becomes contaminated. Urushiol oil can remain "potent" on surfaces for up to five years after it contaminates them.

Protective gear, if you intend working around the stuff, would include disposable barrier clothing (like a rain suit), gloves, respirator, hat and eye protection, at a minimum. Many people afflicted with skin reactions from poison ivy swear by hot water treatments, once the initial contact exposure advice of dousing the area with cool water in the first 15 minutes after exposure is no longer possible. And benadryl brings some systemic relief of the histamine reactions to many, as lilywing13 mentions.

My sweetie points out that any detergent soap will work. Dawn dish detergent, for instance. I was being my usual crunch granola self with the Bronner's recommend, but damn, I love that stuff.

Zanfel. It's expensive as hell, but it works. The other thing I do is when I know I'm going to be exposed, I wear long pants & a long sleeve BUTTON DOWN shirt. This is important - I have had poison ivy all over my face from taking a T-shirt off and I do not recommend it. When I come in I shuck my clothes immediately, put them in a plastic bag and seal it and toss it in the laundry. Then I get into a hot shower right away and Dr. Bronners all over several times. Knock on wood, but it's now been about 3 years since I've gotten bad poison ivy and I used to get it every summer, all summer, systemically: once or twice so bad that I had to go get steroids and cortisone shots at the emergency room. Also, I keep the zanfel on hand just in case, use jewelweed soap and occasionally take homeopathic poison ivy pills. Something's working, but I don't know what.