With treatment, a cold sore outbreak should go away within 5-10 days. If you experience cold sores multiple times per year, you may be a candidate for a daily preventive medication that can help you have fewer and less severe outbreaks.
Outbreaks can be triggered by exposure to sunlight, having a menstrual period, stress, injury to the skin where the cold sore appears, other illness, or dental work. Avoiding these triggers, when possible, can help reduce the number of outbreaks you experience.