When lips lose moisture, the skin covering them can become tight and crack or become flaky, sometimes resulting in sore and even bleeding lips. Unlike other parts of our body, our lips do not contain oil glands, which means they are more likely to become dry. Other factors then exacerbate the situation.
So, a lack of moisture makes matters worse, whether this is weather induced or a failure to moisturise lips manually, and frequently licking lips actually removes moisture too. Extreme weather conditions, like cold or dry air, wind and Sun exposure, strip moisture, and also lead to chapped lips.