On average, how long will a cold sore last when treated with toothpaste?

7 to 10 days: If a cold sore occurs it will usually heal by itself in 7 to 10 days. I do not know of any tooth paste on the market that promotes early healing. There are some over the counter ointments that may shorten it by a couple of days. If it is on your lip it may be a viral infection, then the only thing that can shorten the 7 to 10 days period is a prescription antiviral agent taken early on.

Antiviral: Try antiviral zovirax (acyclovir) rx, or abreva/lysine otc / homeopathic remedies may also help.

Won't help: Toothpaste won't help. Abreva which is otc may help. Homeopathic remedies may also include lysine. Other meds, such as, zovirax (acyclovir) is available with a prescription.