Cold sores are a viral infection of the lip or mouth caused by a herpes virus. Once a cold sore occurs, the person will be susceptible to them for the rest of their lives. The herpes virus is transmitted by contact with infected saliva and lives on the skin and awaits the opportunity to cause trouble. The opportunity arises when the lip is damaged in any way - by wind, sun or physical injury - a crack appears and in jumps the virus causing the appearance of a cold sore.

Mouth ulcers are sore raised areas occurring inside the mouth due to local infection, allergy, injury or the use of some drugs. They are white or yellow with an inflamed outer edge. They are usually positioned on the margin of the tongue or inside lips and cheeks. They will disappear alone in about a week, but treatment can speed this up.

Teething pains start almost any time after the age of 3 months and will continue for several months, or even years, depending on whether or not the eruption of the back teeth is also painful. Common symptoms of teething include; bulging, red gums which are very tender to touch, the cheeks may be hot and red, the child will also be restless, irritable, and may be suffering from a raised body temperature. Teething pain symptoms are often accompanied by the symptoms of a mild respiratory infection i.e. catarrh and congestion. It is not known whether teething causes this or whether the conditions just frequently occur together.