Cold sores, otherwise known as herpes labialis, are sores on the lips and mouth caused by herpes simplex virus (most commonly type-1; HSV-1). Infections typically occur after direct contact with a sore, although asymptomatic transmission can occasionally occur.[1] After an initial episode, the virus remains dormant in sensory nerves, and about one third of people go on to experience recurrent episodes, which can be caused by factors like stress, hormonal changes, fever, UV light, and certain medications.[2] Cold sores are distinct from canker sores, which are caused by a variety of reasons and are not contagious.
