Campho-Phenique cold sore gel is a maximum-strength medicated formula. It's specially made for use on cold sores & fever blisters. Campho-Phenique gel stops the pain and promotes healing. It provides temporary relief of pain and itching due to insect bites and minor skin irritation, associated with cold sores and fever blisters. It also offers first aid to help prevent infection. For best results, use in the early stages of a cold sore.