What causes them
(HealthDayNews) -- Cold sores -- small reddish blisters on the lip -- may be unsightly, but they aren't serious.
Cold sore blisters may form in little bunches, and are caused by the herpes simplex virus, a common viral infection.
According to The Nemours Foundation, most cold sores disappear without any special treatment. But if they're itchy or uncomfortable, you can wrap some ice in cloth and hold it over the sore. Also, avoid citrus drinks because they might irritate your mouth.