Poison ivy grows vigorously throughout much of North America. It can grow as a shrub up to about 1.2 m (4 ft) tall, as a groundcover 10-25 cm (4-10 in) high, or as a climbing vine on various supports. Older vines on substantial supports send out lateral branches that may at first be mistaken for tree limbs.
Poison ivy is apparently far more common now than when the Europeans first entered North America because it has profited immensely from the "edge effect", enabling it to form lush colonies in such places.
The reaction caused by poison ivy, urushiol-induced contact dermatitis, is an allergic reaction. For this reason some people claim to be "immune" to its "poisonous" effects. However, sensitivity can develop over time. For those who are affected by it, it causes a very irritating rash. If poison ivy is burned and the smoke then inhaled, this rash will appear on the lining of the lungs, causing extreme pain and possibly fatal respiratory difficulty. If poison ivy is eaten, the digestive tract and airways will be affected, in some cases causing death.
Dead poison ivy still has plenty of urushiol and will cause the same effect.
You can see pictures of what poison ivy looks like through the 4 seasons here Click Here
