They may have a reaction to it. My feeling is that you should follow the instructions that are given to you when you get your new tattoo. If a problem does happen, do not be afraid to seek help from a medical professional. Not everyone takes care of their tattoos the same way. Each and every tattoo shop has basic ways of doing things, but they incorporate their own ways of taking care of a fresh tat.
Some places say to use vaseline.
Some places will put plastic wrap on a fresh tattoo so that folks won't be peeling back their dressing to look at the tattoo. Other places will tell you that can harm you. So, you see, there is atleast as many ways of taking care of a new tat as there are tattoo artists out there. This is just what has worked for me, personally, to keep my own tats looking as if they were done yesterday. I had my reasons for picking this tattoo.