According to WebMD, a rash from poison ivy can only be spread through the oil of the plant. Contact with any part of the plant, such as the leaves, stems and roots, or touching any item such as clothing or pet fur that comes into contact with poison ivy also causes the rash. The blister fluid does not spread the rash.
Poison ivy often grows along riverbanks and is found throughout the United States except in the Southwest, Alaska and Hawaii. The oils enter the skin quickly. According to MedlinePlus, poison ivy is one of the most frequent causes of skin rash among children and adults who spend time outdoors.
The symptoms of poison ivy rash include red streaks on the affected area, itching, development of hives and blisters containing fluid. People who are allergic to the plant's oil can develop severe symptoms including trouble breathing, swelling of the face and large fluid-filled blisters. To stop the rash from spreading, MedlinePlus recommends washing the oil from the affected area within 30 minutes of exposure and using a brush to remove the oil from underneath fingernails. The rash usually lasts from 10 days to three weeks, but severe cases may last up to six weeks.