Cold sores is a viral infection that causes rashes on the lips. It is a very frequent skin condition, also because it's highly contagious. The virus remains active in the nerves of the skin, allowing the infection to be reactivated again. This usually occurs in case of a poor immune system, illness or sunburn.


Cold sores are caused by the Herpes simplex virus (HSV) type 1. An infection with this virus can be contracted by kissing or sweaty skin contact, at the moment when the cold sore is active. Once the skin has healed again, the virus cannot be transferred anymore. Outside the body, the virus can only survive briefly. After infection, it takes two days to two weeks (on average one week) before the first symptoms occur.
Most people are already infected with this virus as a child. Once infected, one will not easily lose the virus and one can always re-develop a cold sore during periods of illness or poor immune system.


Cold sores create a burning, tingling sensation on or around the lips, followed by painful vesicles, which transform into scab-covered sores after a few days. The vesicles are two to seven millimeters in size. Healing of the skin takes seven to ten days. Sometimes, the cold sores are accompanied by apathy or a feeling of mild fatigue. During the acute phase, the cold sore is contagious. Washing hands after touching the vesicle or sore is therefore necessary in order to avoid infection, as well as avoiding oral sexual contact. Moreover, cold sores don’t only occur just on the lips, but also cheeks, eyes, chin, nose or even shoulder or femur can be affected.


The diagnosis of cold sores is usually made by the patient on the basis of the signs and symptoms. The general practitioner makes the diagnosis solely based on the story of the patient and physical examination. Additional tests are usually not performed. A culture of the bottom of a vesicle can demonstrate the type of herpes virus.


There is currently no treatment to kill the Herpes simplex virus or to prevent a recurrent infection. However, there are medications to reduce the symptoms and the effects of the infection. In particular, the severity of the attack may be reduced and also the number of days that a person suffers from cold sores can be shortened. Uncomplicated infections require basically no treatment.
In patients with a poor immune system or in patients with frequently recurrent infections, an anti-viral agent may be taken. This drug, however, only works if administered early in the infection, preferably when no skin defects are visible yet. In case of severe pain, a painkiller may be used.
If skin defects are visible, they can be dried with zinc oxide cream. Zinc, however, causes a white cover on the wounds and is cosmetically unacceptable for many patients. Lubricating an aciclovir-containing cream or gel can shorten the duration of the sores. Another possibility is to paste a transparent patch with hydrocolloid. The latter works just as well as aciclovir gel, but is cosmetically and hygienically more attractive.


The prognosis of cold sores is good. After more than a week, it has been cured. However, the virus is carried lifelong and the condition can recur in a period of poor immune system. In adults, a cold sore is not dangerous. In babies and young children, however, infection with cold sores may be life-threatening. For them, the immune system is not yet well developed and the herpes virus can cause meningitis. Cold sores can also cause genital herpes.