Licking your lips may seem like an easy way to moisten things up, but it actually does more harm than good. Lips usually lack the protective outer membrane found on most other skin, so adding moisture that easily evaporates seconds later creates a vicious cycle that can dry lips out very quickly.
There's another dark side to lip licking -- saliva, despite its clear, watery appearance, is not akin to pure mountain spring water. Along with teeth, saliva is one of the first mechanisms in the digestive process and it contains enzymes that begin to break up food. Those same enzymes, while so helpful when you want to chow down on a big, juicy burger, unfortunately have a similar effect on the lips: They get a jump-start on digesting them. Biting is no good either, it can damage and weaken tender lips.