Poison ivy, poison oak, and poison sumac are plants that cause a
rash in those allergic to them. This rash is caused by a
chemical in the sap. About 50%-70% of people are sensitized to
this chemical and are, therefore, allergic. Virtually everyone
will eventually become sensitized if repeatedly exposed. Poison
Ivy Rash Copyright © Nucleus Medical Media, Inc. The allergic
reactions to poison ivy, oak, and sumac occur when sensitized
people come in contact with urushiol oil. This oil is found in
the roots, stems, leaves, and fruit of the plant. This oil is
released if the plant is damaged or bruised. If not washed, oil
from these plants may stay potent for years on clothing, tools,
toys, and other items, especially in dry conditions. A risk
factor is something that increases your chance of getting a
disease or condition. Sensitized people are at risk if they: The
main symptom of poison oak, ivy, or sumac is an intensely itchy,
red rash. The rash appears within 24-72 hours of exposure to the
oil. The rash often