I'm a teenage thumb sucker and i'm trying to stop. recently though, i've noticed the i bite my thumb more than suck. what are the health dangers?

Infection: Infection is a danger if you are biting your thumb nail. Are you biting the thumb itself? If yes- basic trauma can occur. Consider cognitive behavioral therapy or behavior modification if you would like to work on extinguishing those behaviors.

Habits-hard to break: Besides just lowering your overall "coolness" rating among your friends there are not a lot of health risks. That is unless you break the skin on a regular basis as that could lead to skin infections Long term changes in your skin could occur with possible changes to your nail Usually this is a stress reliever so maybe you can try substituting something else in it's place?? http://www.wikihow.com/Stop-Sucking-Your-Thumb-%28Older-Kids%29