Cold sores are small blisters that develop and appear around the mouth area. Filled with fluid, they are caused by the herpes simplex virus (HSV-1) and are passed directly from person to person through physical contact. If you have been infected, it is unlikely that symptoms will appear straight away. Instead the virus will remain dormant (inactive). An outbreak of cold sores can occur at anytime, and the frequency of outbreaks will differ from one individual to another. Antiviral treatment like Valtrex, Famvir and Aciclovir can help to reduce the healing time of an outbreak and relieve the uncomfortable symptoms.