[YEA] My vanity for white teeth found me reaching for the peroxide 16 years ago. A side affect was that I was no longer experiencing cold sores (approx 6 a year). My regime was brushing teeth, gums, and tongue with peroxide a couple times a week. When I forgot to do this, the tingling sensation of an outbreak reminded me to do the peroxide treatment and no cold sore surfaced. There have been a few times that I was out of peroxide and got the cold sore but it was gone within 2 days of getting peroxide and the sore was very mild. Apply directly in addition to brushing the entire mouth. I've had two cold sores in the last 15 years. The one during my divorce and the other after getting unjustly fired from my job. Both were mild attacks.