Love (and lust!) is in the air. That's good news for dull winter complexions, as it turns out that a Valentine's Day tryst isn't just helpful for your mood—sex is great for your skin, too. The naturally aerobic activity increases blood flow, bringing much-needed oxygen to your skin cells and imparting your visage with a rosy, fresh-faced flush. Here are the many seductive reasons why sex is great for your skin.