Frequent licking of lips is one of the many causes of dry or cracked lips. Another one is the toothpaste you are using. Try to use toothpaste with no sodium lauryl sulfate or fluoride free. Extreme Weather also makes our lips dry and cracked. During winter the weather is cold and windy that makes our lips dry. Make sure to drink lots of fluids especial water during the day for hydration and wearing lip balm contains aloe Vera protects your lips. Rubbing a cucumber slice on your lips daily for about 10 minutes is also known to be effective.