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Small blister on the lips may be small, but it doesn’t take much to be a nuisance. Lip blisters, or cold sores, may appear as a single, painful sore or in a cluster. Cold sores then break open, leak a clear fluid and crust over. These small lip blisters will heal within about two weeks.
Lip blisters and cold sores are caused by the herpes simplex virus (HSV). Most oral herpes outbreaks are caused by HSV-1. Despite the association with herpes, this virus is often acquired through non-sexual means (a casual kiss, sharing a drink, etc.) during childhood. Less commonly, HSV-2—the strain responsible for most genital herpes outbreaks—causes oral symptoms when passed through oral sex.
STD testing can diagnose small blisters on the lips. Testing for oral herpes and genital herpes is recommended since both strains have similar symptoms. Herpes testing looks for the presence of antibodies in the blood and can be performed with or without symptoms.
When caused by the herpes virus, outbreaks can be controlled through antiviral medication. Daily medication can suppress the virus, which prevents subsequent outbreaks.