I think jealousy stems from not having a secure enough relationship with your significant other. My husband and I are not that jealous, but I think it's because I KNOW him and he KNOWS me. We spend plenty of quality time together and always show and speak our love to each other in little ways. Actually, when we go out, I love how he turns heads - he's gorgeous! It always make me laugh when we walk through the Youth Department and church and all the teeny-bopper girls turn around as he walks by. I remember being that age and having a crush on older men. It's kinda cute to think of my husband as that crush to a young girl.
Edited to add: We NEVER EVER put ourselves in a compromising position with the opposite sex though. A male coworker who is also a friends with my husband asked me out to lunch the other day. I said as long as his wife or a coworker was there, I'd love to, but otherwise, I might be better to wait for another day to get a bigger group. He respected that and I honored my husband in the longwhile. I don't need someone seeing me with a male coworker having lunch thinking it's an affair. I would never put myself in that position. I love my husband too much to even allow gossip to come up.