darkbignate

I'm a photographer, and for an assignment, I want to fake a heroine injection, but obviously I don't want to make anyone inject heroine. I want my subject to actually pierce the skin with the needle, but not inject anything, but if it slips, I don't want him to get sick. what can I put in the needle that won't actually harm him if it is injected? could I possibly get a saline, or something sterile from a doctor/hospital? I want it to look real, so I want the needle to actually pierce the skin, I've gotten many suggestions against it though.