Do you lick them a lot? Bite at them? Pick at them?

Do you drink/nibble a lot of citrus?

Have you tried vitamin E on your lips at all? Smells hideous but it helps with the skin a great deal.

Tried changing toothpastes maybe? Some people find that affects them. I've heard people have good luck with lanolin unless you've tried that too. Only other things I can think of is a deficiency in vitamins somewhere, a necessary change to your diet needed, or maybe stress. :x Have you considered going to a dermatologist?

Have you tried medicated lip balm? My lips have always been uber-dry for no discernible reason and that's the only stuff that stops it. Blistex makes a nice little three-pack that I really find useful.

Sorry :(

Does the rest of your skin tend to be dry as well? Or is it just your lips?

Maybe vitamin deficiency?

Vitamin B2 (riboflavin), Vitamin B1 and Vitamin B6 help provide moisture to lips and if you're deficient in these you may suffer from dry lips. Find B vitamins in pork, liver, whole grains, cereals, nuts, bread, eggs, and milk. On the other hand, too much Vitamin A - taken in supplements, prescription medications or the diet - can lead to peeling lips, which can make them dry and irritated. Check with a pharmacist or doctor if you suspect your vitamins are causing your lips to react.

Dry lips may be also a sign of Anemia (or iron deficiency) and/or early stage diabetes. Better consult a doctor soon!

Breathe through your mouth a majority of the time? Taking any medications? I think if you've tried a lot of average remedies and they didn't help at all then you should go to a doctor about it.

Out of nowhere my bottom lip started splitting right down the middle. I'm not even a mouth breather, and I would probably die if I didn't have chapstick on 24/7 lmao so I was so confused what the hell was going on. I went and bought Aquaphor Lip Repair. This stuff is made of miracles. The very next day the crack had healed and it hasn't happened since. I think it works because it is SO THICK. It just doesn't come off, so that helps keep the lip from being exposed. The only downside is I feel like I will probably never be able to use any other chapstick again because they all seem to just disappear now lol.