This needs to be increased during hot weather. One of things that many people do when their lips feel dry is to keep licking them in an effort to moisturise the lips. In most cases, however, this doesn't solve the problem but makes matters worse. So try not to do this. Sometimes it's irritation from saliva, lipstick, or foods causing a minor allergic reaction that is responsible for these symptoms.
Contact eczema is another cause.
Over-working, stress, tiredness, recent infection all lower the immune system making minor infections around the mouth and lips more likely. These can dry the lips out and the corners of mouth are commonly affected. Eating a healthy diet rich in vitamins C, E, and B vitamins, and also zinc, iron and beta-carotene, together with plenty of rest and regular exercise will help keep the immunity fighting fit. There are some medical conditions where dry lips are one of the symptoms so if the problem persists despite these simple measures then ask your GP for further advice. Visit our extensive Ask the Doctor library of all previously asked questions and answers covering a wide range of topics.