Cold sores, also called fever blisters, are most likely to appear on the outside of your mouth and lips. They are typically caused by the herpes simplex 1 virus..
You can use Zygone™ whenever you notice an irritation. But if blisters form, you may notice that they break and ooze. A yellow crust or a scab builds up and eventually falls off, revealing new skin underneath.
The sores can last for up to two weeks without treatment and can spread to other people until they crust over completely
THESE SELF HELP TIPS ARE NOT INTENDED TO REPLACE THE ADVICE OF YOUR DOCTOR
(Collected from a number of home remedies resources)