Leaves of three, let them be! You've probably heard that little
rhyme about poison ivy. But did you know that poison ivy, poison
oak, and poison sumac all contain the same rash-causing
substance? It's urushiol, a colorless, odorless oil (or resin)
contained in the leaves of the plants. Signs and Symptoms of
Poison Ivy Urushiol is considered an allergen because it causes
an allergic reaction — which takes the form of a rash, itching,
and sometimes swelling. About 60% to 80% of all people get a
reaction to urushiol, which can appear within hours of contact
or as much as 5 days later. Typically, the skin becomes red,
itchy, and swollen and blisters will appear. After a few days,
the blisters may become crusty and start to flake off. The rash
from poison ivy takes 1 to 2 weeks to heal. When to Call the
Doctor Consult your doctor if your child has any kind of rash,
especially with a fever. If poison ivy or a similar plant caused
the rash, the doctor might recommend cool showers and a soothing
lotion, such as calam