It won't scan after about a month. And yes, it actually works until then. The barcode scanner reads the white spaces between the black. If you design the tattoo around an actual products code it works. My friend still has a barcode for Marlboros on his wrist.
i have personaly seen this in person in walmart and the cashier was curious and she scanned it and it said item not found or something like that. it was a pretty big barcode and it was on the back of his head, of course he was bald to.