Cold sores, sometimes called fever blisters, are groups of small blisters on the lip and around the mouth. The skin around the blisters is often red, swollen, and sore. The blisters may break open, leak a clear fluid, and then scab over after a few days. They usually heal in several days to 2 weeks.

Cold sores are caused by the herpes simplex virus (HSV). There are two types of herpes simplex virus: HSV-1 and HSV-2. Both virus types can cause sores around the mouth (herpes labialis) and on the genitals (genital herpes).

To help relieve pain and speed healing:
•Rinse your mouth. Use salt water; baking soda (dissolve 1 teaspoon of soda in 1/2 cup warm water); or a mixture of 1 part — such as 1 teaspoon — diphenhydramine (Benadryl) to either 1 part Kaopectate or 1 part Maalox. Be sure to spit out the mixtures after rinsing.
•Dab a small amount of milk of magnesia on your canker sore a few times a day.
•Cover canker sores with a paste made of baking soda plus a small amount of water — just enough to make a paste.
•Try over-the-counter products that contain the numbing agent benzocaine, such as Anbesol and Orajel.
•Avoid abrasive, acidic or spicy foods that can cause further irritation and pain.
•Apply ice to your canker sores by allowing ice chips to slowly dissolve over the sores.
•Brush your teeth gently, using a soft brush and toothpaste without foaming agents, such as Biotene, Sensodyne ProNamel or Rembrandt Canker Sore.