What is a cold sore?

What is a cold sore?

A cold sore is a fluid-filled blister (or a cluster of blisters) that appears on the lips and around the mouth. Cold sores are also called fever blisters, oral herpes or herpes labialis.

Cold sores are those annoying little blisters that appear and seem to linger on your lips. They are caused by the common and highly contagious herpes simplex virus that many are exposed to in childhood.