The pimples turn into blisters. When the blisters burst, the area around them becomes an open sore. Some people also get a fever. Your skin returns to normal within about a week to ten days. You usually get cold sores on one side of your mouth and in the same place each time.

Some people get warning symptoms about two days before their blisters appear. You may have an itching, burning or tingling feeling on your lips.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.