Question: My daughter gets poison ivy very easily. I try to keep it out of the yard, but she seems to get it anyway. Could she be catching poison ivy from our dog? If so, how can I prevent this?

Answer: Only about 15 percent of adults the United States do NOT have an allergy to the Rhus plant group. This group poison ivy, found mainly east of the Rockies; poison oak, found primarily west of that mountain range; and poison sumac, found mostly in Florida and the Northeast. If you are allergic to one plant, you are allergic to them all.

When these delicate and easily damaged plants receive even light trauma, an oil known as urushiol can leak out on to the plant surface. Contact with this oil causes the allergic reaction. Your dog’s tail whacking one of these plants would certainly be enough to cause urushiol to ooze out.

If your dog then carried the urushiol back to your house and your daughter touched his contaminated fur, she could, indeed, contract poison ivy. In this example, your dog’s fur would be what’s called a “fomite.” This is a technical term for any inanimate object that can carry a disease causing substance or organism. Fomites can also include shoes, clothing, shoes, tools, even the ash in smoke from burning the leaves.

Regardless of how the oil gets on your skin, within 15 minutes it can bind to skin proteins, and the allergic reaction begins. If you wash the oil off before this binding occurs, you may be able to prevent the reaction. However, the oil on fomites or dead plants can still be active for up to five years.

Once the allergic reaction has started, it can range anywhere from mild to severe. Itching is the first symptom, followed by a blister like, vesicular rash and finally oozing, weeping sores. The rash is often in streaks that form lines in the affected area. It can be widespread or localized, depending on where the oil contacted your body.

Some people are highly allergic to urushiol oil and within four to eight hours develop a debilitating rash and facial swelling. This is a true medical emergency and should be referred to the nearest emergency room without delay.

Treatment is aimed both at relief of the itching and at calming down the body’s overreaction to the urushiol itself. Steroids are used to calm down the immune system. These may be either topical ointments applied at the site of the rash or a more systemic approach using pills or shots. If the lesions have become infected, than an antibiotic is also indicated.

Contrary to popular belief the oozing fluid from the blisters will not spread the rash either to another part of your body or to another person. If you break your blisters, however, it does make them more prone to infection.

The number one treatment for poison ivy is prevention. If you come in contact with the plant oil, wash it off within 15 minutes. Hot soap and water is preferred -- but solvents such as acetone, gasoline or rubbing alcohol poured over the affected areas can dissolve the oil. If a solvent is used, it should be washed off immediately. All contaminated clothing should be washed and non-washable items treated with solvents. Pets should be washed. There are products available for use prior to exposure that offer some protection to the skin. Wearing protective clothing is highly advisable.

"Family Medicine" 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. Past columns are available online at http://www.FamilyMedicineNews.org.