Sure it's good for easing muscles, but your sack is more of an organ than a muscle. I've got an idea, how about you read the label? Does it say anything about not applying it to the genitals? Then don't... otherwise you should be fine. And icy hot doesn't give off real heat, so it's not going to destroy any sperm in that sense, I'd be more worried about the chemicals in it if I were you.