Poison wood: avoid it like the plague if you are sensitive to it.  The colour of the leaves can vary from pale green to dark green and even purple, often with black spots on the older leaves.  The plants above are small, but they can grow much taller.  The active compound is urushiol which is used traditionally to make Japanese lacquer - by convicts at one time, I believe.  Brushing against the plant leaves a deposit on the skin, which leads to an unpleasant skin reaction.  Since the compound is oily it is not very easy to wash off, but using concentrated shampoo, body-wash, or washing-up liquid seems to work very well for many people, if applied promptly after contact.  An antihistamine cream (such as Banophen) seems to help a lot too.  I am not sensitive, but I did have some itchy bumps from cutting a lot of it down whilst setting a run.