Time to break out the mistletoe! Here are 4 reasons why kissing is incredibly healthy for you: First: Kissing's good for your teeth. Kissing increases saliva production and according to the Academy of General Dentistry, excess saliva helps break down plaque. It also contains minerals that help rebuild tooth enamel. Another benefit of kissing: It boosts your metabolism. Exercise physiologist Bryant Stamford says that kissing increases your heart rate. And, as your heart beats faster, it releases adrenaline - which DOUBLES the number of calories you'd be burning if you weren't kissing. You'll live longer. Researchers at the University of Arizona found that kissing reduces levels of the stress hormone cortisol. It also lowers levels of bad cholesterol. In fact, couples that kiss goodbye every morning live an average of 5 years longer than those who don't. Finally: Kissing makes you look younger. Facial surgeon Dr. Gus McGrouther points out that kissing tones 30 different muscles in the face and neck. So, it's a fun and easy way to prevent wrinkles and double chins.