Typically these occur on the lip. As soon as you notice one coming up, sometimes a peculiar taste and tenderness will appear before any swelling does, apply heat to the area. You may cut a hole the size of the fever blister in a heavy sheet of paper and heat it with a hair dryer. Or carefully heat a spoon on a curling iron.
Apply it as hot as you can tolerate it for a minute. The heat kills the virus and arrests the development of the sore. You can completely
eradicate your fever blisters especially if you catch it quick enough.