May 15, 2007 By Martha A. Simpson, D.O. Professor Of Family Medicine 4 min read

Question: My children get poison ivy every spring and summer. I have never gotten it, so I don’t know much about it. I worry that I will get it from my kids – or am I immune since I have never gotten it. What do you think? Answer: Only about 15 percent of adults in the United States do NOT have an allergy to poison ivy or the other members of the Rhus plant family. Poison ivy’s close kin in this notorious plant family are poison oak and poison sumac. Generally if you are allergic to one of these plants, you are allergic to all of them. Also, just because you’ve never had an allergic reaction to one of these plants doesn’t mean you’re immune for life. You can develop an allergy at any time.

The Rhus plants are delicate and easily damaged by simply brushing up against a leaf or stem. When such an injury to a plant occurs, a substance called urushiol oil leaks out. It is this oil that causes the allergic reaction.

While these plants are delicate, the oil is quite the opposite. It’s very hearty and can survive away from the plant for several years. The oil can attach to your clothes, a ball that’s rolled into a poison ivy infested bush, or a pet that roams free outdoors. If you then touch one of these objects or play with your pet, you can get a poison ivy reaction even though you did not come into direct contact with a damaged plant.

Regardless of how the oil gets on your skin, it binds to skin proteins in about 15 minutes, and the allergic process begins. If you can wash the oil off quickly, you can prevent the allergic reaction. Once the allergic reaction has started, it can be anywhere from mild to severe. Itching is the first symptom, followed by a raised, blistery rash which doctors call a vesicular rash. These blisters can then burst and turn into weeping sores.

The rash is often in lines or streaks and can be widespread or localized, depending on where the oil contacted your skin. You can also spread it by touching the oil on one part of your body and touching another part of your body. For instance, your leg brushes up against a poison ivy plant, and then you touch your leg and pick up some oil. When you then scratch your eyelid a rash may develop around your eye. Contrary to popular beliefs, however, poison ivy does not spread from person to person through the weeping sores.

Some people also have severe systemic allergic reactions causing a debilitating rash and facial swelling, usually within a few hours of coming in contact with the urushiol oil. This is a medical emergency and anyone who experiences such a reaction should go to the nearest hospital emergency department.

The best treatment for poison ivy is prevention. As soon as you have been exposed, you should wash the exposed area with hot soapy water. If you know you catch poison ivy easily, carry some hand sanitizer with you in the woods, and use it if your skin becomes itchy. There are also products available for use prior to exposure that offer some protection to the skin.

It’s also a good idea to wash your clothes and clean off your shoes every time you have been in the yard or woods – even if you don’t think you’ve come into contact with a member of the Rhus family. Wearing long-sleeved shirts and long pants when outside can also help to minimize skin contact with poison ivy.

—

Family Medicine(r) is a weekly column. To submit questions, write to Martha A. Simpson, D.O., M.B.A., Ohio University College of Osteopathic Medicine, P.O. Box 110, Athens, Ohio 45701, or via e-mail to begin readerquestions@familymedicinenews.org readerquestions@familymedicinenews.org end

. Medical information in this column is provided as an educational service only. It does not replace the judgment of your personal physician, who should be relied on to diagnose and recommend treatment for any medical conditions.

Past columns are available online at www.familymedicinenews.org.