What does poison ivy (or, oak) oil look like?
Urushiol oil has a slight yellowish-green tint to it. But, only when there is a large quantity of it. The amount needed to cause a reaction in most people is so small it is not visible. For example, the head of a pin can contain enough oil to contaminate 100 people. In most cases, it will be invisible to the naked eye before or even after the rash has appeared.