What are cold sores?
Herpes Simplex Virus (HSV) is a virus that infects mucous membrane cells and exists in two forms;HSV I that infects the lips, mouth and face, and HSV-II that infects the genitals. A cold sore is the result of an infection with HSV I and early warning signs of active virus include a tingling sensation on the lips or face. If untreated at an early stage the virus will multiply rapidly and within 24 hours a cold sore will form, starting as small blisters on the surface of the skin, which join up to form a weeping sore. This is when the virus is contagious and can spread to form more cold sores or can infect others by direct contact. Eventually the immune system kicks in to kill the virus and the cold sore crusts over to form a scab as it heals.
Once infected with HSV it is always possible that re-infection will occur, as the virus can persist undetected by travelling down a nerve fibre and lying dormant or inactive in a nerve cell, to be reactivated under certain conditions, such as by stress, illness, sunlight or a compromised immune system.
Treatments for cold sores
Acyclovir is an antiviral drug that can be used to treat infection with HSV-1. It is a nucleoside analogue, which means that it becomes incorporated into the viral DNA within the host cell and replaces building blocks needed for viral DNA synthesis. This inhibits the action of viral DNA polymerase and prevents normal viral DNA synthesis, without affecting normal processes of the host cells, which prevents the virus replicating and therefore stops the growth and spread of the virus. If applied to the skin within 24 hours of the first tingle, acyclovir can prevent a cold sore from developing. However, it can be used at any stage of infection, to prevent spread of infection, reduce and relieve painful symptoms, and speed up the heeling process to help heal blisters and sores caused by the infection. Acyclovir can also be taken orally to suppress recurrent infection of HSV and to prevent infection in people who are immunocompromised. Valacyclovir is a similar antiviral to acyclovir and is a prodrug of acyclovir that is more readily absorbed and is converted to acyclovir by the liver.