After reading so many people saying glycerin cured their bottom chapped lip, I felt it was unethical for me to leave this forum without posting my experience.
After 2 years of suffering, I accidentally discovered the problem was glycerin through the process of elimination with natural toothpastes. It finally came down to silica and glycerin as the only two common denominators in the natural toothpastes versus the ProEnamel, and I was still having problems. Hardly the silica is likely I thought, and it brought me back to a recent memory of trying to make a natural lip gloss out of boiling beetroot in food-grade glycerin thinking it would be "nourishing" for my stressed dry bottom lip. When I put it on my lips, it kind of burned or itched. Thinking it was the acid in the beetroot I never continued with it. Also, as a side note, my teeth became totally sensitive almost overnight 2 years ago. After getting glycerin away from my mouth, my teeth are no longer super sensitive. In fact, they are not sensitive at all. Took about 14 days for this sensitivity pain to go away. I make my own dry powder paste:
2 T. of Arrowroot powder (for natural foaming)
1 T. calcium Bentonite clay (for remineralizing the enamel)
1 T. calcium phosphate powder (optional)
5 drops of clove essential oil (soothes tooth nerve)
10 drops cinnamon essential oil (anti-bacterial/fungal - optional though, as clove has antibacterial/fungal properties too)
Now I eat sugar, drink coffee, orange juice......zero pain. Like being a kid again, and my mouth has NEVER been healthier! Commercial toothpaste is truly cheap crap.
Suffice it to say, glycerin is in EVERYTHING I used, and it was in fact what I was allergic to. Once I stopped putting it anywhere near my lips, my bottom lip returned to normal. Two long years of suffering and not knowing. Bottom lip raw in places, peeling and super dry. Just know that GLYCERIN may not be the answer or the cure for you personally. If you are trying this, and your lips are not getting better, eliminate the glycerin. More and more people are becoming allergic to it, because the manufacturers put it in EVERYTHING, so we are constantly exposed.