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If you’ve noticed a blister around your mouth, it’s normal to ask, “What does a blister on my lip mean?” Fortunately, we have the answer and can help make sense of this symptom. A lip blister—often called a cold sore or fever blister—is generally red and painful. This sore will break open, leak a clear pus and then scab over. Cold sores heal within a few weeks without treatment.
The standard lip blister or cold sore is caused by the herpes simplex virus (HSV). There are two strains of this virus: HSV-1 and HSV-2. Most cold sores are caused by HSV-1, a common and harmless virus affecting millions of people in the U.S. Many people hear the word “herpes” and think of STDs; although cold sore infections are referred to as oral herpes outbreaks, most cases are contracted through non-sexual means, such as a casual kiss or from sharing a drink.
HSV-2 causes similar symptoms, however it is mostly present in the genitals. This strain is responsible for most genital herpes outbreaks. Occasionally, this strain can be transferred to the mouth via oral sex.
Oral herpes testing is recommended in diagnosing a lip blister. A type-specific herpes test can diagnose whether the sore is caused by HSV-1 or HSV-2. Herpes testing is performed through a simple blood test and results are available in about 3 days.
Antiviral medication can suppress herpes virus and prevent outbreak from recurring. When a lip blister is present, over-the-counter medication can alleviate symptoms. If positive for oral herpes (HSV-1), normal sexual activity can take place. However, oral sex should not take place when an outbreak is present to avoid transferring the infection to the genitals.