Many people get a rash from poison ivy, poison oak, and poison sumac. This rash is caused by an oil found in the plants. This oil is called urushiol (you-ROO-shee-all).
The itchy, blistering rash often does not start until 12 to 72 hours after you come into contact with the oil.
The rash is not contagious and does not spread. It might seem to spread, but this is a delayed reaction.
Most people see the rash go away in a few weeks. If you have a serious reaction, you need to see a doctor right away. Swelling is a sign of a serious reaction — especially swelling that makes an eye swell shut or your face to swell.
If you have trouble breathing or swallowing, go to an emergency room immediately.
POISON IVY PREVENTION
Plastic bags are your friends —
use plastic or heavy shopping bags to pull plants from the soil, replacing the bags with the pulling of each plant. Plastic bags can also be used to cover arms for additional protection during the removal process.
Get to the root —
any lingering shoots or seedlings can be killed with white vinegar.
Cover up —
keep skin as covered as possible to avoid any potential contact. Wear long-sleeved shirts and pants.
Rinse, rinse, rinse —
after removal or exposure to poison ivy, rinse any exposed skin with water immediately (avoid soap or harsh scrubbing), and wash clothes immediately.
Reference: American Academy of Dermatology