Cold sores are often preceded by a tingling or burning sensation. The sores start as painful clustered blisters on a red, swollen base. They primarily occur on or around the lips and mouth (“herpes labialis”) but can also occur elsewhere on the face. Once a blister has appeared, it generally lasts from 24 to 48 hours before ulcerating and forming a crust. The crusting may remain for 5 to 7 days, but it generally heals without scarring. Complete healing may take 7 to 10 days. A cold sore recurrence (outbreak) in a person with a fully functioning immune system will normally resolve on its own, although treatment can shorten the length of the outbreak, speed up healing, and reduce viral shedding. Untreated lesions in immunosuppressed people can last for weeks or months.[1][2][3][4][5][6][7]
Cold sore stages (adapted from Semprini 2019[8]):
| Stage | Symptoms |
|---|---|
| 1. Prodromal | Affected area may itch and tingle. Not present in every case. |
| 2. Redness | Some skin redness and swelling. May itch and tingle. |
| 3. Blistering | Small, fluid-filled blisters that start out clear and turn yellow. May be painful. |
| 4. Cold sore | The blisters ulcerate into an open sore. Painful. |
| 5. Crust | A scab-like crust forms over the cold sore. |
| 6. Healing | The crust flakes off to reveal healing skin beneath. |
| 7. Healed | Skin is entirely back to normal. |