I pulled weeds Saturday and now I've got poison ivy up both arms

I wore gloves. Then I pulled them off with my bare hands. — Weekend gardener, 1996

Poison ivy likes the modern world. In a six-year experiment in North Carolina's Duke Forest, plots given extra carbon dioxide grew it 149 percent faster. Good for the ivy. That's one study, and a long survey of a Wisconsin forest found it declining, so nobody should call it settled. The oil that does the damage can stay on a glove for years. Last summer's gloves can still give you the rash. Wash the skin with soap and water soon after contact and you may stop it. Wait, and all you can do is make it milder. The plant doesn't care either way. Neither did you, until Sunday.

For now: wash the skin gently with soap and water as soon as you can, within half an hour if possible, then wash the gloves and tools too.

The full file

Maine's forestry department says the oil can stay active for many years, even after the plant dies. A toxicology society puts it at up to five years on an object, citing a federal safety institute, and the Mayo Clinic says it can stay potent for years. Jackets, tools and shoes all count.

Wash gently, though. The American Academy of Dermatology warns that scrubbing can rub the oil in, and that it hides under your fingernails. The rash shows up a day or two later, says Mayo, and can last two or three weeks.

The Duke team also found the plants made more of the most allergenic form of the oil, up 153 percent in that form. A 45-year survey of a Wisconsin forest found poison ivy was the only woody vine that had decreased. One of the Duke researchers called it "a remarkably understudied species." Nobody has settled it. Wash the gloves.