The lips may undergo changes in size, color, and surface. Some of these changes may indicate a medical problem. Other changes are harmless. With aging, the lips may grow thinner.
Lip sores (ulcers) have various causes. A lip sore with hard edges may be a form of skin cancer (see Types of Oral Cancer Mouth and Throat Cancer Mouth and throat cancers are cancers that originate on the lips, the roof, sides, or floor of the mouth, tongue, tonsils, or back of the throat. Mouth and throat cancers may look like open sores... read more 
; see also Lips and Sun Damage Lips and Sun Damage Sun damage (see also Overview of Sunlight and Skin Damage) may make the lips, especially the lower lip, hard and dry. People over age 45 and people with light skin who have had extensive exposure... read more ). Sores may also develop as a symptom of other medical conditions, such as erythema multiforme Erythema Multiforme Erythema multiforme is an inflammatory skin disorder characterized by patches of red, raised skin that often look like targets and usually are distributed symmetrically over the body. (See also... read more 
, recurrent oral herpes simplex virus infection Oral infection Herpes simplex virus infection causes recurring episodes of small, painful, fluid-filled blisters on the skin, mouth, lips (cold sores), eyes, or genitals. This very contagious viral infection... read more 
(cold sores), or syphilis Syphilis Syphilis is a sexually transmitted infection caused by the bacteria Treponema pallidum. It can occur in three stages of symptoms, separated by periods of apparent good health. Syphilis... read more 
.
Spots on the lips may occur. Multiple, small, scattered brownish-black spots may be a sign of a hereditary disease called Peutz-Jeghers syndrome Hereditary conditions that cause intestinal polyps 
, in which polyps form in the stomach and intestines. Rarely, smokers develop noncancerous brown spots on the lips near where the cigarette is held. Freckles and irregularly shaped brownish areas (melanotic macules) are common around the lips and may last for many years. These marks are not cause for concern.
Kawasaki disease Kawasaki Disease Kawasaki disease causes inflammation of blood vessels throughout the body. The cause of Kawasaki disease is unknown but may be associated with an infection. Children typically have fever, rash... read more 
, a disease of unknown cause that usually occurs in infants and children 8 years old or younger, can cause dryness and cracking of the lips and reddening of the lining of the mouth.
Other common lip changes include
Cheilitis
With inflammation of the lips (called cheilitis), the lips may become painful, irritated, red, cracked, and scaly.
Most commonly, irritation and inflammation involve the lips and skinfolds at the corners of the mouth (called angular cheilitis), typically if the person
Has dentures that do not separate the jaws adequately
Has worn down the teeth excessively, resulting in less space between the upper and lower teeth
Has a Candida or a Staphylococcus aureus infection
Has a deficiency of vitamin B2 or iron in the diet
Treatment consists of replacing the dentures, which helps reduce the folds at the corners of the mouth, or restoring proper tooth size with partial dentures, crowns, or implants. Infections are treated with drugs applied to the corners of the mouth. Vitamin B2 deficiency Riboflavin Deficiency Riboflavin deficiency usually occurs with deficiencies of other B vitamins due to a diet low in vitamins or an absorption disorder. People have painful cracks in the corners of the mouth and... read more and iron deficiency Iron Deficiency Iron deficiency is a common cause of anemia, a condition in which the number of red blood cells is low. Iron deficiency usually results from loss of blood in adults (including bleeding from... read more can be treated by taking dietary supplements.
Other forms of cheilitis usually affect the outside surface of the lips and the lips' border with the skin. Causes include infection, sun damage Lips and Sun Damage Sun damage (see also Overview of Sunlight and Skin Damage) may make the lips, especially the lower lip, hard and dry. People over age 45 and people with light skin who have had extensive exposure... read more , drugs or irritants, allergy, or an underlying condition. Treatment includes petroleum jelly applied to the lips and elimination or treatment of underlying conditions.
