It is not a good idea to have a tattoo when the immune system is not at 100 percent. You’ll need your power and white blood cells to heal your tattoo, something your body won’t be able to do if it already battles viruses and bacteria. Not to mention the fact that bringing your illness into the tattoo studio and risking passing the germs onto others, particularly your artist, is rather inconsiderate. If you have an appointment, call and reschedule once again, when you feel fine.