Well, let me address your question first. Sometimes I crave sugary foods, but as of late I'm seriously trying the no-gluten diet. I'm not longer using any medication or chapsticks, lip balms, etc. I quit brushing with toothpaste and now opt for peroxide rinse and baking soda brushing. I picked up the ideas from searching all over this site. I agree with you. I think it is internal. Matter-of-fact, I'm positive it's internal and an allergy. I've only been on my new plan since the middle of Thursday, but my lips haven't peeled since starting it. They have even passed the water test (wetting lips and no peeling). They've never done this before. I couldn't think of going half a day withouth chapstick. Maybe you should try a no-gluten diet combined with peroxide/baking soda, and no chapsticks etc. I think all of my old chapsticks were contaminated with gluten so using them never helped. Now, I understand the whole "prescriptions work for ten days" then quit thing. They too became contaminated with gluten and would be rendered useless after several days.
I know it's early to call it, but I've never seen these results before. I've already thrown out my old chapsticks. I think I'm going to wait ten days before I try any chapstick like product on my lips again. I must admit to putting neosporin on them today, but I'm not going to do that again in order to continue this test.
Maybe there's some hope out there! I'll keep you abreast of my progress and I hope you do the same.