Poison Ivy is a rash you get from the oil found in the plants poison ivy, poison oak and poison sumac. The rash usually starts 12 to 72 hours after contact with these plants and the symptoms are redness, itching, swelling and blisters. It is not contagious and usually goes away in a few weeks. A dermatologist can make the skin more comfortable during this time period. You should see a doctor immediately if you have a serious reaction such as swelling, trouble breathing or trouble swallowing. If you have trouble breathing or swallowing you should go to an emergency room.