Medical Encyclopaedia › Herpes (short definition)
In brief: Cold sores are caused by herpes simplex virus type 1. After the first infection, the virus remains in nerve ganglia for life and can repeatedly trigger painful blisters on the lips. A large proportion of adults carry the virus.
Course of an outbreak
An outbreak is often heralded by tingling, tightness or burning on the lip. Grouped, fluid-filled blisters then form, which burst, crust over and heal without scarring after about one to two weeks.
Triggers
Typical triggers are colds and fever, strong sunlight, stress, injuries to the lip and hormonal changes, for example during menstruation.
Treatment
Creams with antiviral active substances such as aciclovir or penciclovir can shorten healing somewhat if they are applied early, at the first tingle. Special cold sore patches cover the blisters and protect against transmission. In the case of frequent or severe outbreaks, immunodeficiency or involvement of the eyes, tablets and medical treatment are necessary.
Avoiding transmission
The fluid in the blisters is highly contagious. During an outbreak, kissing, sharing glasses or towels and touching the blisters should be avoided. Newborns and people with atopic eczema in particular must be protected. Lip care with UV protection can prevent sun-related outbreaks.
Related terms in the encyclopaedia
Aciclovir, Lemon balm, Shingles, Atopic eczema
Sources
- IQWiG: gesundheitsinformation.de – Gesundheitsinformationen des Instituts für Qualität und Wirtschaftlichkeit im Gesundheitswesen
- Bundesministerium für Gesundheit: gesund.bund.de – Nationales Gesundheitsportal
Note: This article is for general information and does not replace advice, diagnosis or treatment from a doctor or pharmacist. Last updated: October 2026.