You need to maintain adequate hydration. Drink at least 1.5 - 2.0 litres of water every day. Avoid alcohol and smoking. Try to have a healthy diet schedule and eat lots of fresh fruits and vegetables. Take multi vitamin and mineral supplements especially Vitamin B complex and zinc to make up for any deficiencies in your diet.
Use a medicated sunscreen lip balm so that the damage due to sun exposure can be avoided.
Hope this helps.
iam writing this with utter depression. Iam having dark lips especially my upper lips as am fair my lips are been clearly shown out been dark.iam a regular user of lipstick and i doubt it might b becoz of the low grade lipsticks that i used caused my lip have this bad condition, but the case is like now thw colour is permanent. am really sad..... my upper lips are darker and the for the lower lips half the lower lip is darker and the rest is normal. somebody plz.. help and suggest a cure out and really suffering...