The most common deformities are cleft palate and hare-lip. The former results from a failure of closure of the hard palate and is usually to one side of the mid-line. Hare-lip is the result of failure of union between the superior and premaxillary bones. May be single or double. The tongue may be either unusually large or small. Lack of development of the symphyses of the lower jaw sometimes occurs.

The lips may be the seat of ulcers and fissures and sometimes of a chronic inflammation with thickening.

Anemia of the mucous membranes of the mouth and lips is commonly seen in cases of general anemia and is a well recognized symptom.

Active hyperemia is found in inflammations and as an early symptom in certain infectious diseases. Passive hyperemia occurs in the general congestion of chronic lung and heart disease. Actual bleeding is found in scurvy and purpura and sometimes in the infectious fevers.