Cold sores (fever blisters) are blisters that appear on the lip or around the mouth. They cause the skin around them to become red, swollen, and sore. The sores break open and leak a clear fluid, which scabs over. The time it takes for a fever blister can take up to a couple weeks. Cold sores are caused by the herpes simplex virus and will usually go away on their own.
Over the counter (OTC) options include topical medicines that are applied to skin. Viractin (tetracaine) and Zilactin-L (lidocaine) are applied to the sore to reduce pain. Abreva (docosanol) and Zilactin (benzyl alcohol) can shorten the time it takes the cold sore to heal. Herpecin-L (dimethicone with sunscreen) can reduce pain and prevent cold sores from coming back. Common side effects of these medications include mild stinging, burning, or itching at the application site.