If it has three leaves let it be. Most of us have run into it at one time or another and it sucks. Just a little swipe from a leaf can make you miserable. Once it gets one place and you start to itch it, it spreads rapidly. From your face to your toes to your legs to your everywhere it doesn’t discriminate. If you are allergic it makes it even worse. The oils from the leaves are what causes the itches and the scratching. Some people can experience blisters as well as increased bloating of their arms or any part it comes in contact with. You really got to be careful what you scratch cause some places are a LOT more sensitive than others and can be a lot more painful (I think you know what I mean). If you get it try your best not to itch it, you can use ointments, you should shower and you can put rubbing alcohol on it to counteract the oils.
Below is an image of poison ivy and what happens when you get it on your face: