Cold sores last for as few as 2.5 days if treated with Abreva when the cold sores first appear, according to the Abreva website. The site reports the median healing time for cold sores treated with Abreva as 4.1 days and recommends discontinuing use of the product after 10 days.
WebMD explains that the herpes simplex virus causes cold sores. Application of Abreva to cold sores helps alleviate the pain, burning, itching and tingling that accompany the sores and helps the sores heal more quickly. Abreva blocks the virus from entering unaffected skin cells and multiplying, but it does not inhibit transmission of the virus from one person to another. It also does not prevent cold sores from recurring.