There are a few things you can do for Poison Ivy/Poison Oak/Poison Sumac. One of the best is to make a tea of Jewelweed. Let it step at least 20 minutes. When it cools enough to stand it, soak a cloth in it and apply to the affected areas. You can leave the cloth on the areas as a poultice if you want. It will relieve the itching, and dry the oil in a matter of hours.
Grindelia tincture applied directly to the affected area is also quite effective for most people. Other herbs that work well with direct application are Black Walnut Leaves, Burdock, Mugwort, Mullien, Sweet fern, and Yerba Sante. Most of these herbs can be found within a 10-foot radius of the Poison Ivy plants, so direct application of the juice as soon as possible, in the field, will give the best results.
An effective Homeopathic Treatment is a 6X solution of Rhus Tox, taken internally.
To relive the itching, and shorten the suffering time, you can apply a paste of oatmeal directly to the affected areas.
These methods can be used in combination with each other. Of course, it is important to thoroughly wash the affected areas with Ivory, or Naptha soap as soon as possible. If you are allergic, you should see a physician as soon as possible in case corticosteriods, or antihistamines are needed to prevent anaphylaxis. If in doubt, see a physician ASAP.