the causes of this problem are very wide-ranging and so are the specific characteristics of this condition.
some people got it after taking certain medicines, others got it after having suffering of stress/anxiety/depression.
some got it after eating too much wheat, others got it because they licked their lips a lot.
some got it for no apparent reason.
some of us only feature excess keratin production, thick scabs forming. others also have inflamed lips that hurt and some of us have some white slimy substance forming on their lips.
some of us have digestive problems, other have psychological issues. some have both, others have none.
some cured this by changing their eating habits, others left their lips alone as much as possible and got cured.
some forgot about the problem and it went away, others took antidepressants and it cleared up.
occasionally, this just went away for no apparent reason.
the lips are a very very sensitive area with lots of nerves. these nerves seem to respond to things going on in our body in strange ways. some processes in our body (our mind can also be involved) seem to make the lip nerves freak out and make the lips produce a lot of keratin instead of normal lipskin. once this cycle is triggered, it's very hard to be reversed.
all in all, i would say that this is not a dangerous disease in any way.
however, it can be an indicator for other issues in our bodies.