How can contact with poison ivy, oak, and sumac be prevented?
Poison ivy and its relatives are often hidden among other vegetation. Even if you know exactly what they look like, it is very hard to avoid coming in contact with them. Although wearing long pants and long sleeves in warm weather may be uncomfortable, it is important to do so when you might be in contact with plants you can't see, whether you are gardening in the backyard or hiking in the woods. So-called "barrier creams" may help a bit but are not very effective.
When pulling up weeds, those who may be allergic should make sure to tuck sleeves into gloves at all times, since sleeves tend to ride up the forearms and leave wrists and forearms exposed. Vinyl gloves do not absorb the allergen in poison ivy (urushiol) well and are, therefore, more effective for prevention than fabric or leather gloves.
If you think you may have been exposed to poison ivy, wash the skin with soap and water as soon as possible. After half an hour, however, this is no longer likely to prevent the reaction. As discussed above, washing pets and clothing may also be of limited help.
Attempts to desensitize people by immunotherapy (giving them poison ivy by mouth or by injection) were tried in the past but proved to be ineffective and potentially dangerous.
What should people do if they are exposed to a poisonous plant?
If you think you may have been exposed to poison ivy, wash the skin with soap and water as soon as possible. This is often not practical because it must be done immediately to have an effect. After half an hour, however, this is no longer likely to prevent the reaction. As discussed above, washing pets and clothing may also be of limited help. It is important to remove and wash your clothes as well as to wash any gardening equipment, tools, or other items that may have come into contact with the plants.
Medically reviewed by Norman Levine, MD; American Board of Dermatology
Stephanides, Steven L., and Chris Moore. "Plant Poisoning, Toxicodendron." eMedicine.com. Aug. 18, 2009. <http://emedicine.medscape.com/article/817671-overview>.