Well, this is not news here. Alex has six tattoos but they do not make appearances on TV during Moonlight when he plays vampire P.I. Mick St. John. Here is part of a write up from Moonlightline.com about the great ink cover up:
O’Loughlin obviously has to conceal some of his body art as he portrays detective Mick St. John on Moonlight given his vampire nature. However, there was a bit of a slip-up during the episode The Ringer in which the back of his shirt flew up and cameras got a glimpse of his lower back tattoo.
Meanwhile, meticulously covering up his tattoos is just one of the things O’Loughlin has to endure on the supernatural series. He also has to wear special fangs and creepy lenses, and go through long days of shooting just to deliver a good show.
Personally I think Mick’s character would be even “cooler” if he had some tats. 😉