Kissing can ruin lives. Lips touch sometimes teeth clash. New hunger is born with a throb and caution falls away. A cursed girl with lips still moist from her first kiss might feel suddenly wild like a little monsoon. She might forget her curse just long enough to get careless and let it come true. She might kill everyone she loves...
There are other ways of showing someone you love them, such as fetching them out of Hell.
Interview de Laini Taylor (en anglais)