Poison ivy, poison oak, and poison sumac can generally be identified by their clusters of 3 shiny leaflets. DON'T TOUCH OR INGEST THEM! LET THEM BE! LET THEM BE! Some sighs include itching of the skin and blisters. If you come in contact with this plant you could take an oatmeal bath which may help, but you should really seek medical treatment at once.
Notice in this picture of a poison ivy in the fall that there are 3 distinct leaflets attached to the stem.