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Phases of a cold sore

There are 4 main phases to the life cycle of a cold sore. The herpes simplex virus is contagious during every one of these phases. Together, the 4 phases typically run 7 to 10 days, but can sometimes last up to 2 weeks or longer. It’s important to contact your doctor once a cold sore lasts for more than 14 days.

Phase 1: The Tingle Phase (days 1-2)
Before any visible cold sore appears you may experience some unusual sensations around your lips and mouth that indicate a cold sore is about to develop. This phase is commonly called the “Tingle Phase” and about 70% to 75% of people may experience these initial symptoms. Usually, you can feel the skin tightening in the area where the cold sore is about to develop. As a reaction to the infection, the area becomes red and swollen. Even at this early phase, the infection is contagious. So avoid close, physical contact if you feel a cold sore coming on.

Phase 2: The Blister Phase (days 2-4)
This is the phase where the cold sore blisters appear. The area turns red and painful. Clusters of small blisters are formed, which can grow into one large blister. The blister is fluid and contains millions of virus particles.

Phase 3: The Ulcer Phase (days 4-5)
Typically the most painful, the ulcer phase happens once the blisters burst. This phase is when you develop an open sore and it is the most infectious phase.

Phase 4: The Healing Phase (days 5-10)
The blisters dry up and a crust forms that is yellow or brown in colour; it forms a scab. As the scab shrinks, you may experience painful cracks that can bleed. A series of scabs will form over the sore, each smaller than the previous one, until the cold sore is completely healed.

Phase of a cold sore:

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