Ask An Expert: Poison Ivy

Content provided by the Faculty of the Harvard Medical School

Ask An Expert: Poison Ivy

Question:

Can poison ivy spread from person to person?

Answer:

An oil called "urushiol," found within the sap of the poison ivy plant, is what causes the rash of poison ivy. The rash is an allergic reaction to the oil. A similar reaction can occur to urushiol found in poison oak and poison sumac. Touching the plants puts you in contact with the oil.

Once you remove the oil from your skin by washing, you will not transfer the oil to others. Remember, the oil causes the rash, and wherever the oil touches, a rash may develop.

Many people wonder if they are spreading the rash when new areas develop. Unless they are again coming in contact with the oil, they are not spreading the rash. Some areas of skin may react to the oil sooner than others. New areas of rash may develop for one or two weeks after the original exposure to the oil.

Even indirect exposure to the oil can lead to a rash. This includes touching a gardening glove or a pet that has touched a poison ivy plant. Even coming in contact with airborne particles of urushiol, caused by burning poison ivy plants, can lead to a rash. Learn what poison ivy, poison oak and poison sumac look like, and avoid them. See your doctor for treatment if a rash develops.

Rebecca Campen, M.D., J.D. is an Assistant Professor of Dermatology at Harvard Medical School and former Deputy Director of the Harvard/Massachusetts General Hospital Cutaneous Biology Research Center (CBRC). She currently serves as Senior Advisor to the CBRC and divides her time between clinical practice of dermatology at the Massachusetts General Hospital and private practice in Savannah, Georgia. Dr. Campen is the author of two books for medical students and residents, Going Into Medical Practice and Blueprints in Dermatology.

Last updated:	July 16, 2007