acute inflammation. You need inflammation to heal a wound. Acute inflammation heals the wound and it goes away, no more inflammation. Cortisol comes and regulates the inflammation quickly with no side effects.
chronic inflammation. When acute inflammation happens for long(chronic trauma) it becomes chronic inflammation(non healing wound) and this causes chronic cortisol. Thus the side effect.
There is nothing different about the lips. Apart from it doesn't have sweat and hair glands. So it gets dehydrated easily. If i kept picking at a scab somewhere else on my body and aggravate it constantly.. the same effect will happen. The wound won't heal.