Yes, kissing can help you fight off colds and flu! By exchanging bacteria back and forth, you are actually enhancing your body's natural defenses and boosting your immune system. But that's not to say you should go out and give a big smooch to any sicky around you... Up the ante and have sex! Performed once a week, sex has been shown to increase immunoglobulin A (IgA) production, an immune-boosting protein that helps keep pathogens at bay. Get our sustainable sex tips.