Palmer, I feel for you. I'm allergic also , and it can be quite a pain in the a-- when you get that stuff..
Washing up after your done is too late ,contamination can occur within 20 minutes to one hour after exposure. Most jobs take much longer than that. I've used the following preventive steps and have had some success.
No matter how hot it gets wear a long sleeve shirt and gloves. Use ivy-block to protect exposed skin, available at cvs/ekert drug store, on face neck and forearms.
Wash up with soap and water, or hand cleaner. The oils that cause the irritation are not water soluble, rinsing will not wash them away.
Wash cloths and boots w /soap and water. Get this ,if your boots and bootlaces have brushed against the ivy, you can contaminate yourself , and your house when you get undressed at the end of the day. This contamination can be passed on tho your kids and family if the touch anything that you've touched.
If you do get it, go to the Doctor as soon as symptoms appear.
Get the shot in the a--, get the prednisone pills, and any other
medications available.
This year i've tried a homeopathic preventative that is available
thru Sherrill, you take it daily, and it helps your body build an immunity to it.
Beware, it never dies, and the oils can contaminate for up to a year.