Your ankle itches, so you reach down to scratch it and - oh, no! Several small bumps and the beginning of inflammation mean you've gotten into poison ivy. The "poison" in poison ivy, oak, and sumac is a resin called urushiol that is highly irritating to the skin of most people. Because urushiol doesn't evaporate quickly, you can get into trouble not only through direct contact with these plants, but by handling tools or clothing that have been in contact with them - or even by patting the fur coat of a cat or dog that has come across poison ivy in the woods. Firewood that may have been dragged through brush can also be a source of urushiol contact.
Prevention of poison ivy rashes is preferable to treatment. You and your children should know how to recognize poison ivy, poison oak, and poison sumac plants so you can avoid them. Teach them the old "Leaves of three, let it be." It's not infallible, but it helps.
Contact & Tips
If you know you've come into contact with poison ivy, wash with plenty of water (don't use harsh soaps) within five minutes of exposure. When you're out hiking, you might want to carry disposable wipes with alcohol that you can use immediately after contact.
If you have to work around poison ivy (to get rid of it, for instance), consider using Ivy Shield, a barrier skin cream that is available at outdoor equipment stores. Even if you use Ivy Shield for temporary protection, however, you should remember that tools and clothing need to be thoroughly cleaned after contamination with urushiol.
Calamine lotion is the old standard treatment for poison ivy rash, and there are also lots of folk treatments that have never been clinically tested, but time is the only cure. A very intense rash, or one that covers a large area of skin, probably calls for a corticosteroid that must be prescribed by a doctor.