Chapter 2: What Causes These Blisters to Appear?

The most common cause of recurring blisters around the mouth is infection with the herpes simplex virus. HSV-1 typically affects the lips and mouth area, although HSV-2 can sometimes produce similar symptoms. The virus spreads through direct contact, including kissing, sharing utensils, towels, or other personal items. 

Once infected, the virus remains inside nerve cells for life. Certain triggers can reactivate it, leading to new outbreaks. Common triggers include stress, illness, fever, fatigue, sun exposure, hormonal fluctuations, and weakened immunity. 

Not every bump on the lips is herpes-related. Allergic reactions, skin irritation, bacterial infections, and other dermatological conditions can produce similar symptoms. Nevertheless, recurring clusters of painful, fluid-filled blisters are among the most recognizable signs of oral herpes.