Most lenses have a rating for "close-focus" which means the closest distance between the lens and the subject.
For the Canon 18-55 mm lens you have, that "close-focus" is 9.8 inches.
If you want to get closer you need a macro lens. With Canon that will be a native (non zoom) lens.
They can be used for normal portraits as well as macro photography.
Here is a link that shows all of the Canon lenses currently available and their suggested retail prices:
Just click on the lens that interests you and look at the "specifications" for the details.
If you want to see a review of a particular lens here is a good European website for lens reviews: