They typically take the form of tiny, clear, fluid-filled
blisters on the face, most commonly the
lips. They could become painful blisters that ulcerate and crust over. A cold sore usually clears by itself in seven to twelve days, and rarely leads to medical complications.
The number of blisters varies from one to a whole cluster. Before the blisters erupt, the soon-to-be-infected skin may itch or become very sensitive.