Dutch scientists have found an intimate kiss lasting 10 seconds transfers on average about 80 million bacteria. They also found partners shared more similar bacterial colonies than two strangers. Before you insist your significant other swig mouthwash before each kiss, remember, diversity in bacteria can help your immune system response. This similarity did not correlate fully with kissing behavior. A shared lifestyle, environment, and genes also play a role.
PositiveTip: Intimate kissing probably plays a role in bonding and immunization. Keep kissing your partner!