There are basically 5 stages to a cold sore outbreak. If left untreated, cold sores generally take 7 to 10 days (sometimes longer) to heal.

	1. Prodrome This is often called the "Tingle Stage". Up to 60% of patients experience the prodrome stage, which may last from a few hours to a day. Usually there is a feeling of the skin tightening in the area where the cold sore is about to develop, before there are any visible signs. Some people describe it as an itching or burning sensation. The area then becomes red and swollen due to the inflammatory reaction to the infection.
	2. Blister Swelling develops and multiple vesicles or blisters appear. The cold sore blister fills with fluid and contains millions of virus particles. White blood cells travel to the blister to help fight the infection.
	3. Ulcer At this point, the blister usually ruptures, leaving a painful, reddish ulceration. Many patients describe this as the most painful stage of the cold sore. During this stage, the cold sore is most contagious. Remember -- the cold sore should be considered contagious at every stage of the outbreak.
	4. Scab/Crusting The ulcer dries, leaving an unsightly scab or crust that may be visible for several days. Many find this stage painful because activities such as smiling, talking and eating can break the dry scab open. Severe itching and/or burning is also common.
	5. Healing (or loss of crust) As the cold sore heals and the scab starts to come off, patients may experience some dry flaking and residual swelling. Their skin may also remain slightly pink or red. Typically, cold sores heal within eight to ten days, but in some cases they may last much longer.

1. Spruance SL. Herpes simplex labialis. In: Sacks SL, Straus SE, Whitley RJ, Griffiths PD, eds. Clinical Management of Herpes Viruses. Washington, DC: IOS Press; 1995:3-42
2. Raborn GW Pharmacodynamic Considerations in the Treatment of Cold Sores: A comparative Look at Available Treatments. PowerPac CE, Dec 2006

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