Why did I randomly get a cold sore overnight?
Cold sores are caused by the herpes simplex virus. Once the herpes simplex virus is in you, it can cause outbreaks of cold sores. Cold sore outbreaks are often triggered by exposure to hot sun, cold wind, a cold or other illness, a weak immune system, or even stress.
Why did I get a cold sore out of nowhere?
Cold sores are sometimes called oral herpes because the herpes simplex virus type 1 (HSV-1) causes them. This virus is very common and highly contagious. It spreads through saliva or close contact — often through kissing or by sharing utensils, straws, towels or lip balm with someone who has a cold sore.
Can a cold sore appear in one day?
Within 48 hours, a cold sore blister may appear around your mouth or lips, though you can get them anywhere on your face, including around your nose. A cold sore results in a swollen lip as the blister develops.