Hello doctor. An IIT aspirant from kota Rajasthan. I have a problem with my lips. Sort of a skin problem you can say. Half of my lips that is inside and is mostly covered is pink (in a better state) while the part that is outside is very black. I have no idea that how it happened. I have a bad habit of biting my lips. Please help me with your suggestions as it looks very bad and odd while smiling or expressing myself in the open. That's all. Please suggest some steps to overcome this issue. Thank you.