about poison ivy

This is the first year I've really been bothered with poison ivy. My husband never seems to get it. I liked this information article.

"Ask Dr. H - Can you still spread poison ivy even after you've washed?
By Dr. Mitchell Hecht

Q: My doctor says that once you wash off poison ivy sap from the skin, you can't spread it. If that's right, then why is it that whenever I get poison ivy it seems to spread to other areas? -D.C., Philadelphia

A: The skin rash (dermatitis) that causes poison ivy is due to the chemical "urushiol" contained in the plant's sap. All parts of the plant, from the leaves to the roots, contain urushiol. 85-90% of people who come in contact with the sap will get a poison ivy rash. The sap containing urushiol can rapidly penetrate the skin within 10 minutes after contact. Washing your skin within 5-10 minutes with soap and water or even hydrogen peroxide may prevent the rash. The problem is that either we don't know we've brushed against a plant, or the sap is left behind on our clothes to cause a rash days later when we handle them while doing laundry. Urushiol is an oil, and will stick to almost anything - clothing, sports equipment, hiking gear, garden tools- even your dog's or cat's fur.

Once you've developed the rash, you can't spread it to other parts of the body or to another person. That's because once the sap is washed away, there's no more allergen around to cause a rash. Those blisters you see are your body's reaction to a foreign substance on the skin. Blister fluid does not contain any sap and therefore can't spread the rash. New lesions that appear a few days after the initial rash are just less sensitive skin areas or areas where there was less sap exposure - not a spreading of the rash."