To cold sore sufferers, the ultimate benefit of Zeno CS is that it can actually eliminate a cold sore as opposed to just shortening its duration. Preventing the blister from forming and thus eliminating the cold sore is possible but you have to be prepared. For the best results you must apply the Zeno CS at the very onset of symptoms and use it according to the directions. A 4-minute treatment, applied every 4 to 6 hours, ends most cold sores. In clinical trials, most cold sores healed in 3 days or less.